Montesquieu: Strategist ahead of his time

ABSTRACT

Montesquieu’s many works contain a sophisticated account of military strategy that anticipated nineteenth-century developments in the subject. In particular, his influence over Jomini was more significant than previously realized.

KEYWORDS:

• Montesquieu
• strategy
• Jomini
• Clausewitz

Charles-Louis de Secondat, Baron de La Brède et de Montesquieu (1689–1755) was a man of rare achievements. Today he is chiefly remembered for his views on the legal separation of governmental powers, which ultimately found expression in the US Constitution. Yet he has also been described as a pioneer in the fields of sociology, anthropology and comparative politics. He was in fact an important, if somewhat controversial, individual within the French Enlightenment. And as was frequently the case in his day, he was an intellectual generalist who ranged confidently across a wide variety of subjects that engaged his interest. One of these subjects was war, about which he had a great deal to say. It figures prominently in his most important work, The Spirit of the Laws (1748), and in his Considerations on the Greatness of the Romans and their Decline (1734). It also features in his satirical novel, Persian Letters (1721), and his posthumously published Reflections on Universal Monarchy.¹

Montesquieu had no personal experience of war, his profession being the law. Nor does he display an intimate familiarity with the standard military authorities of the times. His writings pay scant attention to the likes of Vauban, Feuquières or Follard who were then supposed to reside on the bookshelves of every well-educated officer.² That said, his father had been a soldier and he himself maintained close friendships with some notable military personages. One of these was the colourful Claude Alexandre, Duc de Bonneval (1645–1747) who fought with distinction under Prince Eugene of Savoy before converting to Islam and entering Ottoman service.³ According to Montesquieu’s biographer, Robert Shackleton, the two were thick as thieves after their paths crossed in Vienna in 1728.⁴ Another such friend was the Jacobite general James FitzJames, First Duke of Berwick (1670–1734). The two initially met when Montesquieu was seeking his way in Parisian society, and they remained close until Berwick’s fatal encounter with a cannon ball at the siege of Philippsburg during the War of Polish Succession.

We know that military matters were a topic of conversation with Bonneval, and frequently so with Berwick.⁵ In the eulogy to Berwick that Montesquieu later wrote, he declined to pronounce definitively on the quality of his friend’s generalship citing a lack of requisite expertise.⁶ And yet in an earlier passage, he had praised Berwick’s resort to interior lines of operation during his defence of the provinces of Dauphiné and Provence against the Duke of Savoy in 1709. ‘M. le Maréchal’, we are told, ‘conceived a plan of defence such that it was impossible to penetrate into France, from any side whatsoever, because he occupied the cord of the arc that the Duke of Savoy was obliged to make’.⁷ Clearly, therefore, Montesquieu understood enough of military methods to recognize something of merit when he encountered it. He was far from ignorant in this regard.⁸ As we shall find, moreover, his understanding of war extended well beyond questions of operational technique. Not only did it encompass the moral and technological dimensions of military power, but also the wider benefits and risks of resorting to war, and what they implied for the policies of states towards each other.

In due course such matters would be grouped under the rubric of strategy, but in Montesquieu’s day this was not yet the case. Before the nineteenth century war was rarely studied in so holistic a fashion. Instead attention generally focused on tactical and logistical details.⁹ Not until Antoine-Henri Jomini and Carl von Clausewitz do we find conceptions of strategy that are comparable with Montesquieu’s in terms of the breadth of their concern. This makes it suprising that Montesquieu has attracted little attention from historians of strategic thought. Christopher Coker and Beatrice Heuser have touched on his writings.¹⁰ Scattered allusions to his influence on Jomini and Clausewitz have long existed, and Azar Gat has more recently added to the picture in this regard.¹¹ Nevertheless, Montesquieu’s views on strategic matters have not been subject to systematic study. In what follows, I address this lacuna with two principal aims in mind. Firstly, I seek to establish Montesquieu’s strategic credentials via an examination of his most relevant ideas; and secondly to ascertain the extent of his influence over Jomini and Clausewitz.

The spirit of the laws

Montesquieu’s key work contains a version of the argument to which most eighteenth-century philosophes in one way or another subscribed: that human society is ammenable to systematic study, and that its dynamics can be expressed in laws analogous to those that demonstrably apply to the physical world. ‘I have laid down the principles’, Montesquieu tells us in the preface, ‘and have discovered that particular cases comply naturally with them; that the histories of all nations can only be their consequences; and that each particular law is linked to another law, or is derived from another more general one’.¹² From an Enlightenment perspective, the significance of such laws lay in what they implied for the remediation of social pathologies. To the extent they could be fathomed, they would provide the blueprint for a just society founded on reason rather than on unchallenged prescription and unexamined tradition. In this manner could humanity think itself free of the mental shackles binding it to an earlier age of ignorance and predjudice. The correct application of reason would inevitably yield the single best way of organizing all human life.

It was on this latter point, however – on the question of solutions – that Montesquieu departed from the mainstream. To the consternation of his fellows, he steadfastly rejected their determinist commitments. He denied the existence of any universally optimum answer to the question of how society should be organized. On the contrary, he was all for variation in accordance with local conditions and believed that efforts to impose some ideal vision on the world could only end in procrustean misfortune.¹³ It is this rejection of absolutes, this championing of the refraction of laws through local circumstance, that provides Montesquieu’s distinctive answer to the question of how people should live, and by extension how they should make war.

Montesquieu begins with his famous definition of laws as ‘the necessary relations that derive from the nature of things’. Mention of necessity might seem to wed him to the determinism he steadfastly rejected, but matters are not that simple. The physical world, he tells us, faithfully obeys ‘invariable’ laws of the kind articulated by Newton; indeed, no such world would be possible in their absence. Humans as physical beings are part of this world and are likewise unfailingly subject to its laws. However, humans as intelligent beings are different in this respect. We are far from perfectly conforming to the equivalent laws that govern our social relations. That we depart from these laws is due both to the limitations of our reason and the influence of our emotions. As free agents, we must each direct ourselves, despite our ‘finite intelligences’ and our tendency to be carried away by ‘a thousand passions’. It is for this reason that societies develop bodies of political and civil law, in order to remind us how we ought to behave.¹⁴ It is in relation to this latter category of laws that Montesquieu’s rejection of determinism came into play. Their content, he maintained, is not the same across time and space but instead reflects the specific combination of circumstances that accompanies the emergence of each individual society. Important in this regard are factors such as a country’s climate, the fertility of its soil, the extent of its territory and other aspects of its physical geography. Together these circumstances, and others like them, impose themselves on societies, in each case creating a unique set of pressures that requires an equally unique set of institutional responses. It is these responses that are ultimately codified into positive laws, making it most unlikely that those relating to one people would suit another. For Montesquieu, the dynamics underpinning these various laws, along with their interrelationships, comprise the ‘spirit of the laws’ as it applies to each particular society along with the state that grows out of it.¹⁵

War and the state

According to Montesquieu, the state is a response to the coalescence of atomized humanity into discrete societies. Individuals in nature, he asserts, would not be aggressive towards one another. But problems begin once they band together in order to enjoy the benefits of society. Once this happens each society gains a sense of its strength in relation to others. From this flows the concept of domination, and with it the practice of war.¹⁶ How then are the benefits of society to be preserved in the face of its tendency to encourage war? The solution lies in the emergence of centralized authority, in the form of the state. It is the state that organizes the collective strength of its people in order to generate the military power necessary for deterring or fighting wars. To this extent all states are the products of a common imperative, namely the provision of security from external aggression. Typically, however, Montesquieu, does not consider this imperative to be determinative of the character of states. On this point he explicitly disagrees with Hobbes who had previously made the provision of security an apology for authoritarianism.¹⁷ Whilst important, security for Montesquieu is but one imperative amongst many requiring mutual accommodation in accordance with the spirit of the laws. Each state, in other words, must make provision for war, but must do so with regard to its own particular set of circumstances.

Unique as each result is, Montesquieu nevertheless stipulates that states can be divided into three basic types. This division, he maintains, is founded on the nature of a state’s government along with its associated ‘principle of action’. The nature of a government arises from its structure, whether republican, monarchical or despotic. The principle of a government refers to the specific ‘human passion’ from which it derives its motive force. A republic is governed by the people (or a fraction thereof), and its principle is virtue: a preference for public over private welfare. A monarchy is governed by a king and its principle is honour, which consists in public acknowledgements of esteem. And a despotism is governed by the fiat of a single individual, its principle being fear. Montesquieu does not claim that a state is driven by one passion to the exclusion of all others. Humanity, it will be recollected, is too often at the mercy of a ‘thousand passions’ for this to be so. Nevertheless, the principle of a state may be regarded as the mainspring of its action. Whether virtue, honour or fear predominates, it is the task of government to harness it to the policy goals of the state, which include those for which wars are conducted.¹⁸

Here once again we find local physical conditions exerting an influence on institutional developments. Montesquieu maintains that despotism is common in Asia because there are relatively few geographical barriers to state expansion. Extensive plains are interrupted relatively infrequently by mountain ranges and seas, whilst narrow rivers make only modest obstacles. This allows states to grow so large that they require despotic rule to function at all. There is no opportunity for prior debate if political decrees are to reach remote territories in a timely manner, and only fear can command the loyalty of distant governors. In contrast, the geography of Europe serves to partition it into smaller units that can more readily acquire republican or monarchical form.¹⁹

The conduct of war

The foregoing account of state formation might be considered an exercise in political philosophy that (interesting as it is) bears little relevance to the concerns of strategists. In fact, however, it is central to Montesquieu’s distinctive views on strategy. For not only does the spirit of the laws, as it applies to each particular society, account for the character of its associated state. It also governs the interactions between states, including those associated with the conduct of war.

According to Montesquieu, the conduct of war should take its cue from the law of nations (or what we today term international law), which is itself properly founded on two basic principles. The first of these principles is that ‘nations should do as much good in peace, and in war the least possible harm, without endangering their true interests’.²⁰ War, in other words, is not a license to indulge princely passions. It should instead be a rational enterprise in which the use of force is proportioned to the political stakes. Some threats may justify drastic action. The pre-emptive use of force would, for example, be warranted if a ‘people perceive that prolonging the peace would permit another to destroy it, and that attacking is the only way of preventing this destruction’. Small states are more often justified in resorting to pre-emption under these circumstances because their lack of strategic depth renders them less capable of resisting invasion than their larger neighbours. In all cases, however, the defence of ‘true interests’ is the only valid motive for war. For a prince to make war in pursuit of glory is unwarranted because glory is a passion, and therefore does not provide a rational basis for action.²¹

As for the second principle of the law of nations: ‘The object of war is victory; that of victory is conquest; and that of conquest preservation’.²² Here in other words, Montesquieu articulates a means-ends hierarchy that connects success in war to the ultimate fortunes of states. The terms victory and defeat he uses in a military rather than a political sense. To be victorious is to defeat an enemy’s army in battle, and in doing so deprive him of his means of resistance. On this matter, Montesquieu has regard to three different dimensions of warfare: the moral, the operational, and the technological.

The moral dimension

Defeating an enemy army typically involves inflicting casualties amongst its ranks until their will to resist is broken. The collapse of enemy resistance therefore stems from moral as well as material damage. In Montesquieu’s words: It is not usually the real loss suffered in battle (which is to say of several thousand men) that is fatal to a state, but the imagined loss and discouragement that deprives it of the very strength fortune has left it.²³ This implies that the moral basis of resistance is a source of variation in the performance of armies that repays careful consideration. Certainly Montesquieu reflects on the differences soldiers display in terms of fighting spirit, and on this point we see him returning to the influence of geography and climate. The fertility of the soil, he tells us, can exert an important influence on the martial qualities of the local population. Barren regions make for men who are tough, courageous and well suited to the demands of war. This is quite apart from the challenges associated with invading mountainous regions, which are themselves formidible. Not only are mountains readily defended by their inhabitants but they create logistical problems for attacking armies, which must carry all of their provisions with them. On the other hand, fertile soil makes for an easy life that does not harden men sufficiently to make good soldiers of them. ‘It has been remarked’, Montesquieu tells us in this connection, ‘that German troops levied from regions where the peasants are rich, such as Saxony, are not as good as the others’.²⁴ The link traditionally drawn between Prussia’s poor soil and its military prowess would not have surprised him.

The climate of a country likewise exerts a significant influence over the temperament of its inhabitants and thus their suitability as soldiers. Warmer climes, Montesquieu explains (by reference to some interesting physiological theories derived from observations of a sheep’s tongue), make for indolence, timidity and a heightened sensitivity to discomfort. Conversely people from colder regions are less susceptible to pain, making them more vigorous and braver. ‘One must flay a Muscovite to make him feel’ he notes in this respect.²⁵ Still if people from colder climes make better soldiers in general, they do not perform equally well when transplanted to a warmer theatre of war. If one’s soldiers are to fight well, care must therefore be taken to ensure they are not committed under conditions that sap their will.

If we pay attention to the last wars, which remain in our mind’s eye, and in which we can more readily discern subtle effects that would be imperceptible from a greater distance in time, we shall conclude that northern people transported to southern countries did not perform such fine deeds as their compatriots who, fighting in their own climate, possessed all their courage.²⁶

Montesquieu is here refering to the War of the Spanish Succession (1701–14), which embraced the Low Countries and Germany in addition to Spain. There is a sense in which historical events are compatible with his climatic account of martial quality. The Grand Alliance proved successful in the northern theatre, winning the battles of Blenheim (1704) and Ramillies (1706). Further south in Spain, however, it performed less well. The decisive event in this theatre was the Battle of Almansa, in which an Alliance army (including ‘northern’ contingents of English and Dutch soldiers) was badly defeated by a Franco-Spanish force. Still it would be easy to dismiss Montesquieu’s musings on this matter as those of an amchair general, but for one important point: the victor of Almansa was his friend Berwick who would have been an unrivalled source of insights into the battle and its outcome.²⁷

The operational dimension

Despite the importance Montesquieu attaches to moral factors for military performance, he also appreciates that the ability to impose casualties on the enemy rests on the number of one’s own soldiers that can be concentrated for battle. For this reason, he is interested in the relationship between force, space and time in war, and here we find a characteristically eighteenth-century geometrical aspect to his analysis. A state at risk of invasion, he explains, should be capable of rapidly assembling its forces at any point along its frontiers that might be threatened by its neighbours. This leads him to argue that an ideal relationship exists between the size of a state and its susceptibility to defence. A small state lacks strategic depth, which leaves it vulnerable to being rapidly over-run.²⁸ Conversely, a state that is too large will encounter difficulties protecting its territory. This is partly because the further it expands, the greater will be the number of other potentially hostile states it shares borders with. On this point Montesquieu cites the example of Russia’s conquests during the early eighteenth century. Look, he asks us, ‘what neighbours Muscovy has recently given itself: the Turks, Persia, China and Japan. It has reached the frontiers of these empires instead of having the happiness of being separated from them by immense deserts’.²⁹ Additionally, the larger a state becomes the more dispersed its forces will be, and thus the longer it will require to concentrate adequate numbers of them at a threatened point on its frontiers. For these reasons, Montesquieu argues that a state ‘should be moderate in size, so that it is proportionate to the degree of speed that nature has endowed men for transporting themselves from one place to another’. Both France and Spain are, he claims, the ideal size from this perspective. Within their confines, armies can rapidly concentrate and switch from one location to another as necessary.³⁰ From all this, he concludes that a state’s true power resides not in its ability to conquer, but rather in its ability to frustrate its neighbours’ designs in this respect. Although it may be wise for a small state to secure itself by means of territorial acquisitions, prudence demands that this not be pushed too far. No more territory should be accrued than can readily be defended.³¹

Here, Montesquieu anticipates something of Heinrich von Bülow’s famous claim that the size of European states was destined to reflect the logistical considerations hobbling late-eighteenth-century armies.³² But whereas Bülow advances a strictly determinate geometrical relationship between logistical and geographical factors, Montesquieu provides a more nuanced account. The ideal relationship between size and security is not simply a function of physical factors alone, he tells us, but also depends on considerations stemming from a state’s form of government.

As far as republics are concerned, they must remain small if they are to prosper. This is because in small states the interests of the people are more readily discernible. Thus, there is less scope for the abuse of power and its concealment from others. As states grow larger so does the complexity of their affairs. A smaller proportion of the people can meaningfully participate in government, which renders it more vulnerable to special interests whilst abuses of power become easier to hide amongst the complexity. Republics therefore experience difficulties in charting a satisfactory path between two competing imperatives: preserving their territory from invasion, and preserving their domestic political values from dilution. To expand is to endanger the place occupied by virtue in affairs of state, whilst to continue small is to remain vulnerable to invasion and conquest. According to Montesquieu, there is no purely military solution to this predicament. Instead, it is best addressed by the union of several small republics into a larger confederacy. In this manner can each individual republic hope to maintain its internal values whilst contributing to the military power and strategic depth necessary to preserve the confederacy as a whole from external threats.³³

For their part, monarchies can afford to grow larger than republics without incurring the same risks to their internal political arrangements. This is because honour enjoys a more certain grasp on the behaviour of men than does virtue. That said, there are limits to expansion beyond which it is unwise for a prince to proceed. These are associated with the nobility’s tendency to acquire large estates in distant provinces. Too much of this kind of thing removes them from the quotidian experience of monarchical surveillance, which ultimately facilitates dissent. Monarchies should not therefore expand without regard to the internal risks in a bid to protect themselves from invasion. Rather, they should build fortresses to defend their frontiers and ensure their armies contest every inch of threatened territory.³⁴

Despotic states are usually larger than republics or monarchies. This is partly because conquest exacerbates the problems of space and time that ultimately leave fear the sole instrument of government. In such cases, a prince dare not build fortresses to defend outlying provinces because the loyalty of underlings is always suspect, and fortresses can serve as alternative power bases for the politically ambitious. Instead, despots prefer to isolate themselves from their neighbours by laying waste to their own frontier provinces. This scorched-earth approach creates an obstacle to invasion by depriving an enemy army of the resources required to sustain its advance. ‘It is a law of geometry’, Montesquieu reminds us, ‘that the greater the extent of bodies, the more their circumference is relatively small’. Consequently, the large size of despotic states means they can more readily afford to sacrifice their outer provinces than can other governments.³⁵ Nevertheless, despotic states are always potentially fragile in the face of a determined invader. This is because their size militates against the rapid concentration of strong forces in distant provinces. An enterprising enemy that succeeds in traversing its wasted frontiers can therefore look to outnumber any local forces it encounters. And if such forces are defeated, they will automatically be dispersed for want of fortresses into which they can retreat. Thus, the enemy will find its way clear for a dash to the capital whilst the despot’s main forces are still endeavouring to concentrate. Furthermore, a significant threat to the regime may encourage subordinates to pursue their own interests without fear of retribution from the centre. Therefore, an invader may never have to face unified resistance.³⁶

In fine, Montesquieu’s account of the relationship between force, space and time in war transcends purely operational considerations. Whilst it is clearly underpinned by the laws of geometry, it is not determined by them in the strict sense that Bülow would later envision. Instead, the consequences of these laws are inflected by the different natures of the belligerent governments. What is advisable for a monarchy is not necessarily advisable for a republic or a despotism, and so on. What Montesquieu provides us with, in other words, is an account of warfare in which operational matters reflect the political complexions of the belligerent states.

The technological dimension

Just as martial qualities and numbers contribute to the object of victory in battle, so too do the organization and equipment of armies. Consequently, they should reflect this object as faithfully as possible, and Montesquieu develops this point at some length. The Romans, he argues, took particular care to examine their adversary’s arms and armour and adapt their own to meet new threats. Their goal was to ensure that the legions were equipped with the best of everything. One result of this was that the weight of Roman arms and armour increased over time, placing greater demands on their users. Soldiers were therefore subjected to severe training regimes in order to ensure they possessed the requisite strength, endurance and dexterity. Discipline was equally fierce, underpinning as it did the whole process of hardening men to the rigours of battle. In such a manner did the legion become an unusually efficient war machine, superbly adapted to its purpose.³⁷ Montesquieu cites Vegetius’ opinion that only a god could have inspired the Romans with the vision necessary to create such a thing.³⁸ But this is merely the borrowing of a metaphor on Montesquieu’s part. What he himself detects is the influence of reason applied in conformity with the principle that victory in battle is the object of war. Moreover, the advantages accruing to Rome from this arrangement were, he maintains, spectacular. He goes so far as to claim that successive improvements in its military technology constituted the principal factor facilitating Rome’s rise to world power.³⁹

And yet Montesquieu is equally clear that a narrow commitment to technological rationality will not alone preserve the fortunes of a state. There are always other considerations that must be taken into account. In the case of Rome, the military victories made possible by superior technology were harnessed to an imprudent degree of territorial expansion. This went beyond what the institutions of the Republic could bear, and the result was a collapse into tyranny that placed virtue at a discount and proved corrosive of political and military power alike. In respect to this latter point, he cites Vegetius on the loss of discipline within the legions. Under Emperor Gratian the soldiers obtained permission to discard their burdensome armour, thereby leaving them vulnerable in battle and prone to flight. In this manner was Rome’s ultimate decline brought about.⁴⁰ Superior weaponry is therefore no sure substitute for moderation in foreign policy.

Furthermore, Montesquieu entertains decidedly lukewarm views on the role played by technology in the warfare of his own day. The degree of relative superiority achieved by the Romans is, he maintains, no longer possible for a European state. This is because all modern armies are now thoroughly aware of the need to compete in technological terms. Let one of them adopt some innovation and the others are quick to respond in kind.

These days we ceaselessly copy one another. Does Prince Maurice discover the art of besieging fortifications? Soon enough we become skilled at it. Does Coehon change the method? So too do we. Some people use a new weapon and everyone else is suddenly trying it.⁴¹

The effects of this competition he considers a mixed blessing. The invention of gunpowder means that no defences remain impregnable, an implication being that a previous source of restraint on princely ambition has been lifted. On the other hand, he entertains the argument that speedy reduction of defensive positions can make for shorter wars. A key point here is that no single answer exists to the question of whether technological developments are good or bad. Context always matters in this respect. Still in one regard eighteenth-century optimism does succeed in getting the better of Montesquieu. Fearing that some invention might one day furnish means of rapidly destroying nations in their entirety, he comforts himself with the belief that such a discovery would be outlawed by unanimous consent. It ‘is just not in the interest of princes to make conquests by such means’, he maintains, because they desire additional subjects and not territory alone.⁴² The genocidal weapons and politics of the twentieth century he would not have judged to accord with the law of nations.

The verdict of battle

At this point, a brief recap may be in order. The principles underlying the Law of Nations state that the ‘object of war is victory; that of victory is conquest’, and we have seen that victory in battle turns on a combination of moral, operational and technological factors. This leads us to the relationship between the outcome of battle and conquest. And here Montesquieu supplies an additional twist by arguing that not all battles are equally important for the fortunes of states. A clash of arms, it would seem, may do no more than nudge the balance of advantage one way or the other.⁴³ But on other occasions the results can be more far-reaching. In such instances, military defeat leaves the vanquished state incapable of further resistance and therefore susceptible to conquest. Why then this variation in the wider consequences of battles? For Montesquieu, the reason is clear enough. It is no artefact of chance but rather of the extent to which states observe the overall limits of their war-making potential.

It is not fortune that dominates the world … There are general causes, either moral or physical, that act within every monarchy, elevating it, maintaining it or casting it down. All accidents are subject to these causes; and if the hazard of a battle, which is to say a particular cause, ruined a state, there was a general cause necessitating that this state perish through a single battle. In a word the main tendency carries with it all particular accidents.⁴⁴

In other words, the greater the fraction of one’s resources that are committed to war, the more likely will military defeat (should it occur) yield political disaster in the form of conquest by one’s adversary.

Conquest and preservation

For Montesquieu, conquest is not the ultimate object of war. Rather, it is but a means to the ultimate object of preservation. Here in other words, we are given a sharp reminder that war, properly conceived, serves a positive purpose. It may involve destruction, but it should nevertheless be conducted in a manner calculated to maximize whatever gains are to be had. The spirit of preservation should therefore suffuse the victor’s behaviour when it comes to the business of conquest. Whilst conquest may involve the destruction of the enemy state, this does not mean the same fate should be visited on its people. By destroying the enemy’s army in battle, a conqueror has removed any threat to himself and so is no longer justified in visiting death on the people. Where modern publicists argue otherwise, it is because they mistakenly conflate state and people. In fact, the state is an association of people, and not the people themselves. In line with the spirit of preservation, therefore, the appropriate fate for a conquered people is not death but incorporation into the victor’s polity. On such a note of moderation is Montesquieu’s account of the instrumental relationship between war’s means and ends completed.⁴⁵

The remarkable story of Charles XII

Regarding the conduct of war, there was hardly a monarch whose fortunes illustrated Montesquieu’s views so neatly as Charles XII of Sweden (r. 1697–1718). In The Spirit of the Laws he therefore makes events surrounding the fateful battle of Poltava (1709) the subject of a cautionary tale.⁴⁶ Charles combined great tactical skill with more than a little personal dynamism. He was heir to the Vasa dynasty’s reputation for achieving military victories on the back of slender human and economic resources, which had previously raised Sweden to great-power status. The young king exploded onto the European stage at the outbreak of the Great Northern War (1700–21), which was triggered by the alliance of Denmark, Poland and Russia against him. Striking first towards Copenhagen, he handily knocked Denmark out of the war. He then turned east and attacked the Russians at Narva – in the teeth of a snowstorm and whilst greatly outnumbered – virtually destroying the opposition. Next in Charles’ sights was the elected Monarch of Poland Augustus II, whom he deposed in 1704 and finally brought to heel in 1707. Now, after years of campaigning, might have been the time to pause and consolidate; but Russia yet remained in the fight and Charles was therefore determined to advance on Moscow. The Swedes pressed hard into Russia, but their objective was remote and Peter I now resorted to Montesquieu’s habitual expedient of despots: laying waste to the territories along his line of retreat. Running low on supplies, Charles was finally deflected into Ukraine where he impatiently awaited help from Sweden. When the supply train he was expecting was intercepted by Russian forces, he nevertheless decided to renew operations. The result was the Battle of Poltava where he suffered a catastrophic defeat at the hands of Peter. Had Charles been at liberty to apply his formidable tactical ability on the battlefield, things might have gone otherwise. But he had previously been wounded (shot through the length of his foot) on a reconnaissance, and therefore delegated the command of his forces to subordinates. Only when the battle was under way did he seek personally to intervene, in the process disorganizing the Swedish effort.⁴⁷

Poltava proved the turning point of the war. Although hostilities continued thereafter, Sweden’s power steadily ebbed away in the face of a newly assertive Russia. Still for Montesquieu the true significance of Poltava resided in the events that preceded it – events ensuring that Sweden would not fully recover from the vicissitudes of a major defeat. ‘It was certainly not Pultava that ruined Charles’, he tells us. ‘If he had not been destroyed at that place, he would have been at another. The accidents of fortune are easily repaired’. But, he continues, ‘one cannot ward off events that continually arise from the nature of things’.⁴⁸ Charles, in other words, had earlier sealed his own fate by seeking to conduct a long war, against several enemy powers, without the resources necessary to sustain it. By consistently acting against ‘the nature of things’ he exhausted Sweden’s resources to the extent that defeat at Poltava proved the last straw. Even so, Montesquieu does not argue that Charles was necessarily doomed to lose the war. The real problem was that his plans did not accurately reflect the reality of the situation he faced. That situation did not entirely deny him agency, and events might have turned out differently had he revised his plans accordingly. In the event, however, Charles provided a spectacular example of what Montesquieu considered a common failing of monarchs. He was a strong tactician who sought victory on the battlefield without due regard to the strategic dimension of his endeavours.

It is a common thing to find princes who know how to give battle. There are very few who know how to make war, who are equally capable of exploiting fortune and awaiting it, and who, with the disposition of mind that makes for circumspection before an undertaking, fear nothing once begun.⁴⁹

For his part Charles may have feared nothing, but he was evidently incapable of accommodating his ambitions to the play of fortune.

Montesquieu finds an altogether more positive example in the exploits of Alexander the Great. Alexander fought a series of successful wars that took him from Greece to north-west India, conquering all in his path. But grand as his ambitions were, notes Montesquieu, he was nevertheless careful to ensure that he did not reach beyond his means. He proceeded systematically, so that his conquests consolidated his own power whilst detracting from that of his enemies. If on occasion he acted precipitately it was because there was some genuine advantage to be gained from doing so. As Montesquieu puts the matter: ‘if it is true that victory gave him everything, he also did everything to obtain victory’.⁵⁰

Strategist ahead of his time

Montesquieu’s grasp of strategic matters was broad by the standards of his day. Possibly because he was a generalist who cultivated a wide field of vision, his thinking on war was liberated from the concern with technical minutiae that characterized the work of contemporary specialists. Having no personal exposure to the practical problems of campaigning – of training, organizing, equipping, supplying and paying soldiers – he was free to consider hitherto neglected aspects of strategy that tied war to the fortunes of states. Ignorance of the means of war hardly guarantees a clear understanding of the processes through which it realizes political ends. Still for his part, Montesquieu grasped enough of the technical detail to ensure his analysis remained suitably grounded in practicalities.

Montesquieu’s basic philosophical commitments, as embodied in the spirit of the laws, are also important for his views on strategy. He allows that we might formulate propositions that convey something of ‘the necessary relations arising from the nature of things’. Colder regions breed hardier soldiers; the readiness with which force can be concentrated for battle depends on the size of a state; superior technology makes for greater lethality. And yet, he maintains, in no such cases does a determinate relationship exist between cause and effect. Things are never the same for everyone everywhere, with the result that sound strategic decisions can only be founded on a holistic appreciation of the prevailing circumstances. It is in this latter respect – this positing of fundamental dynamics qualified by specific circumstances – that Montesquieu anticipates those more modern, inclusive conceptions of strategy that are associated with Clausewitz and Jomini.

Montesquieu’s influence

Montesquieu may have anticipated later developments in strategic thought, but did he exert any influence over them? Establishing intellectual lines of descent can be a ticklish business. Inspiration comes from many sources, and the same idea may arise independently in different minds. In the absence of explicit acknowledgements it is all too easy to draw unwarranted connections. That said, it is evident that Montesquieu was important for the development of strategic thought in ways that we might readily enough imagine. Azar Gat has demonstrated that he exposed eighteenth-century military theorists to ‘a new depth of connection between all the elements of the socio-political fabric’. In this respect, he found a receptive audience in the Count de Guibert and Henry Lloyd, both of whom he alerted to the desirability of military thought accommodating variation in such matters as national character and type of government.⁵¹ It was evidently through Montesquieu that Guibert and Lloyd learnt to understand war as, inter alia, an extension of politics.

The classic expression of this latter sentiment is provided by Clausewitz, and yet there is limited evidence that his views on such matters owe all that much to Montesquieu. We know that Clausewitz initially considered modelling the presentation of his major work, On War, after Montesquieu because he tells us so. ‘The manner in which Montesquieu treated his subject hovered vaguely before me’, we learn from the foreword.⁵² As Gat has observed, we should be wary of infering too much from such a passing disclosure about presentational matters. Nevertheless, he detects the influence of Montesquieu behind Clausewitz’s well-known theoretical efforts to assimilate the universal and locally contingent aspects of war.⁵³ He also notes that Raymond Aron previously identified a resemblance between Montesquieu’s definition of laws as the ‘necessary relations arising from the nature of things’ and the role Clausewitz allows for the ‘nature of things’ in theorizing war. Moreover, Gat himself makes a plausible case that Gerhard von Scharnhorst provided the intellectual route by which this aspect of Montesquieu’s philosophy reached Clausewitz.⁵⁴

This is perhaps as far as matters can be taken with reasonable certainty. It is, however, tempting to suggest that Montesquieu played some role in inspiring Clausewitz’s trinitarian conception of war. Montesquieu’s views on the role played by passion – governed by reason – as the mainspring of states prefigure Clausewitz on such matters. According to Clausewitz the potential for violence in war reflects the degree of popular passion that is unleashed by hostilities. In absolute monarchies, where war is basically a private enterprise, this does not amount to all that much. Conversely in republics, where war is an endeavour of the people, the passion unleashed is notably greater – as was the case in France during the 1790s.⁵⁵ At any event war’s conduct is not (or at least should not be) left to the dictates of passion, but governed by reason, if it is to be considered an instrument of policy.⁵⁶ The commonality between Montesquieu and Clausewitz looks stronger still if we consider their views on the influence of chance in war. Montesquieu, it will be recollected, does not consider the play of fortune decisive for the outcome of wars in the absence of other contributing factors. All else being equal a resourceful general can look to restore a situation brought about by the hazards of war. Nevertheless, he is clear that chance events (like a general getting shot in the foot) can be important for the result of individual battles and can thereby even precipitate the downfall of a state that is already vulnerable for other reasons.⁵⁷ This chimes with Clausewitz’s sensitivity to the role of chance in war, with his keen appreciation that matters rarely go according to plan, and his view that strategic deliberations should make prudent allowance for such eventualities. In Montesquieu therefore we find arguments that foreshadow Clausewitz’s trinitarian conception of war governed by passion, reason and chance.⁵⁸

What then of Montesquieu’s influence over Jomini? Here, the evidence is rather clearer. Craig Brinton and colleagues long since noted that Jomini’s best-known work, his Summary of the Art of War (1837), might just as easily have been titled The Spirit of the Art of War. For in it we find an insistence that warfare is governed by a fundamental principle – the concentration of force at the decisive point in the theatre of war – whose application nevertheless requires adaptation to the specific circumstances at hand.⁵⁹ For his part, Azar Gat has since adopted a more equivocal position. He argues that Jomini was a practical-minded soldier with little interest in philosophy, and that consequently his writings were not directly influenced by the likes of Montesquieu. Rather, he received the general message of principles adapted to circumstances indirectly via other military authorities, with Guibert and Lloyd being candidates in this respect.⁶⁰ Having said that, Gat also notes that Jomini acknowledged an intellectual debt to Montesquieu in a work that preceded his Summary by some years. This was his Treatise on Grand Military Operations, which we shall consider in a moment.

No doubt there is some truth to the notion of indirect influence. Jomini was familiar with the military literature of the eighteenth century and wrote a valuable essay on the subject.⁶¹ Nevertheless, there is also strong evidence that Montesquieu exerted a direct influence over Jomini’s thinking. Indeed, it would seem he was central to Jomini’s realization that the application of war’s fundamental principle ought to be more than a purely military exercise – that a wider range of circumstances merited consideration.

In the Summary Jomini insists that strategists must apply this fundamental principle in light of circumstances that transcend the operational situation. The first two chapters of the book provide a detailed discussion of the matter.⁶² However, this aspect of his writing had not always been so prominent.⁶³ An important shift came in 1818 with the publication of the third edition of his aforementioned Treatise on Grand Military Operations, in which we find the following passage:

To succeed in great enterprises, it is not only necessary to weigh the comparative strength of the two armies … It is also necessary to know how to judge of the interior condition of nations from what they have had to suffer externally … Neither must we neglect to add to the balance the passions of the people against those with whom we have to contend, their peculiar institutions, and the strength of their attachment to them … In a word it is absolutely necessary to know that science which consists of a mixture of politics, administration, and war; the basis of which has been so well laid down by Montesquieu in his work upon the Causes of the Greatness and Decline of the Romans.⁶⁴

Here, in other words, we find Jomini explicitly acknowledging a role for Montesquieu in alerting him to the broader set of factors that influence the expression of war’s fundamental principle in concrete cases.

It is, moreover, clear that the foregoing passage reflects a key point in the development of Jomini’s understanding of strategy. To appreciate its significance we must pause to consider the historical events that prompted its inclusion in the third edition of his Treatise; for nothing comparable appears in the earlier 1805 and 1811 editions.⁶⁵ By 1818, Napoleon had been conclusively defeated and exiled to St Helena. Jomini therefore needed to explain how the great warlord, whose conduct of operations had so faithfully instantiated the fundamental principle of war, had ultimately been laid low by his enemies. Where had Napoleon gone wrong? It was in connection with ‘that science which consists of a mixture of politics, administration, and war’ that Jomini found an answer, and in doing so expanded his theoretical horizons. He reckoned that Napoleon was probably conversant with ‘that science’ but felt confident enough in his own operational genius to ignore its cautionary implications with impunity. The emperor, Jomini concluded,

fell from the height of his greatness because he forgot that the mind and strength of man have their limits, and that the more enormous the masses which are set in motion, the more subordinate does individual genius become to the inflexible laws of nature, and the less is the control which it exercises over events.⁶⁶

Here, it is likely no coincidence that Jomini’s verdict echoes that of Montesquieu on Charles XII whose disregard for ‘the nature of things’ led him to ultimate defeat.

In short, Jomini’s efforts to understand the downfall of Napoleon led him to Montesquieu. And from Montesquieu, Jomini learnt that strategy involves rather more than concentrating force at the decisive point in accordance with the prevailing operational situation. In this manner was the way paved to the richer account of strategy that Jomini provides in his Summary.

It remains to note that, in his efforts to illustrate the many wider factors that bear on strategic deliberations, Jomini borrowed examples from both Montesquieu’s Spirit of the Laws, and his Considerations on the Greatness of the Romans. Thus, we learn that people living in mountainous regions ‘have always resisted longer than those of the plains, as much because of their character and manners as the terrain’.⁶⁷ We are likewise informed that the growing softness of Rome’s legionnairies ultimately had terrible consequences for Imperial fortunes. These ‘formidable soldiers, who wore helmet, shield and breastplate under the scorching African skies of the Scipios’ days, found them too heavy under the cold skies of Gaule and Germany; then the Empire was lost’.⁶⁸ Such instances serve to confirm the important role played by Montesquieu in the development of Jomini’s thought.

To conclude, Montesquieu’s influence over Jomini was more direct and important than has hitherto been realized. The evidence here is clear enough. And although we possess no explicit confirmation from Clausewitz, it is possible that Montesquieu influenced some aspects of his thinking too. Montesquieu was, therefore, not only a strategist ahead of his time. He was also a source of inspiration behind the development of later strategic thought.

Acknowledgments

The author wishes to thank Beatrice Heuser, Fenella Morris and two anonymous reviewers for commenting on earlier drafts of this article.

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

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John Stone

John Stone is a Senior Lecturer in the Department of War Studies, King’s College London. He specializes in the history and theory of military strategy

Notes

¹ For The Spirit of the Laws (De l’esprit des lois) I have relied on the first four volumes of Oeuvres de Monsieur de Montesquieu, rev. ed. (Amsterdam and Leipzig: Arkstée and Merkus 1757). For the other sources mentioned see: Oeuvres complètes de Montesquieu, Vol. I: Lettres persanes, ed. Philip Stewart, Catherine Volpilhac-Auger, Cecil Courtney, Edgar Mass, Pauline Kra and Didier Masseau (Oxford: Voltaire Foundation 2004); Oeuvres complètes de Montesquieu, Vol. II: Considérations sur les causes de la grandeur des Romains et de leur decadence; Réflexions sur la monarchie universelle en Europe, ed. Françoise Weil and Cecil P. Courtney (Oxford: Voltaire Foundation 2000). Various musings about war also appear in the notebooks in which Montesquieu recorded ideas for future development. See for example, Pensées et fragments inédits de Montesquieu, 2 vols (Bordeaux: G. Gounouilhou 1899–1901), 354–60. Unless otherwise specified translations are my own.

² On this point see Anon., [Charles François Olivier Rosette, Chevalier de Brucourt] Essai sur l’éducation de la noblesse, new ed., Vol. II (Paris: Durand and Pissot 1748), 218–80.

³ Bonneval’s life is recounted in Septime Gorceix, Bonneval Pacha: pacha à trois queues, une vie d’aventures au XVIII^e siècle (Paris: Plon 1953).

⁴ Robert Shackleton, Montesquieu: A Critical Biography (Oxford: Oxford University Press 1961), 103–4.

⁵ For the record of a conversation between Montesquieu and Bonneval on the poor performance of Danish troops in past wars see Pensées II, 359. On Berwick: ‘I often heard him say that the thing he had most desired his whole life was a good place to defend’. Berwick, Mémoires de Maréchal de Berwick, écrits par lui-même, Vol. I (Paris: Moutard 1778), xxxviii with emphasis added.

⁶ The eulogy was never completed, but a draft was included in Berwick’s posthumously published memoirs. Ibid., xvii–xlviii.

⁷ Ibid., xxxvi–xxxvii. Montesquieu’s arc-and-chord distinction is adopted from Berwick’s own account of his defensive scheme. See Berwick, Mémoires See ibid., II, 66.

⁸ Montesquieu learnt of the effectiveness of Berwick’s resort to interior lines in conversation with officers who had been on the opposing side. Ibid. I, xxxvii.

⁹ There were of course exceptions to the general rule. See Beatrice Heuser, The Strategy Makers: Thoughts on War and Society from Machiavelli to Clausewitz (Santa Barbara: CA, Praeger 2010).

¹⁰ Christopher Coker, Barbarous Philosophers: Reflections on the Nature of War from Heraclitus to Heisenberg (Oxford: Oxford UP 2010), 74, 169, 173–4, 176; Heuser, Beatrice Heuser, Strategy Before Clausewitz: Linking Warfare and Statecraft, 1400–1830 (London: Routledge 2018), 169, 173, 181, 187; Beatrice Heuser, ‘Clausewitz, Die Politik, and the Political Purpose of Strategy’, in Thierry Balzacq and Ronald R. Krebs (eds.), The Oxford Handbook of Grand Strategy (Oxford: Oxford UP 2021), unpaginated. https://doi.org/10.1093/oxfordhb/9780198840299.013.4.

¹¹ Crane Brinton, Gordon A. Craig and Felix Gilbert, ‘Jomini’, in Edward Meade Earle (ed.), Makers of Modern Strategy: Military Thought from Machiavelli to Hitler (Princeton: Princeton UP 1943), p. 91; Peter Paret, Clausewitz and the State: The Man, His Theories, and His Times (Princeton, NJ: Princeton UP 1985), esp. 171n; Peter Paret, Understanding War: Essays on Clausewitz and the History of Military Power (Princeton, NJ: Princeton UP 1992), esp. 97–8; Azar Gat, A History of Military Thought: from the Enlightenment to the Cold War (Oxford: Oxford UP 2001). See Book I for references to Montesquieu.

¹² L’esprit I, cxxxvi.

¹³ On his refusal to be ‘a wholehearted determinist’ see Isaiah Berlin, ‘Montesquieu’, in Henry Hardy (ed.), Against the Current: Essays in the History of Ideas (Princeton, NJ: Princeton UP 2013), 164–203.

¹⁴ L’esprit I, 1–6.

¹⁵ Ibid., 12–13.

¹⁶ Ibid., 9.

¹⁷ Ibid., 6–9; John Stone, ‘Thomas Hobbes as Strategist’, Defence Studies 21/1 (2021), 67–83.

¹⁸ L’esprit I, 15–58.

¹⁹ Ibid., 253; L’esprit II, 135–6; Réflexions, 346–8.

²⁰ L’esprit I, 10.

²¹ Ibid., 275–6.

²² Ibid., 10.

²³ Considérations, 118.

²⁴ L’esprit II, 141, 144; Pensées II, 359.

²⁵ L’esprit II, 31–8.

²⁶ Ibid., 33.

²⁷ Berwick provides an account of the battle in his Mémoires I, 391–5. It ought to be acknowledged that it occurred in the April, and Berwick does not mention the heat in this context. Scattered references to the challenges it posed do appear in other passages however.

²⁸ See Montesquieu’s comments on the strategic dilemma of republics below.

²⁹ Réflexions, 360.

³⁰ L’esprit I, 267–8; Réflexions, 360–61; Pensées, 310–12.

³¹ L’esprit I, 269; Réflexions, 360.

³² Anon., [Heinrich von Bülow] Geist des neuern Kriegssystems hergeleitet aus dem Grundsatze einer Basis der Operationen auch für Laien in der Kriegskunst faßlich vorgetragen von einem ehemaligen Preußischen Offizier (Hamburg: Benjamin Gottlieb Hofmann 1799).

³³ L’esprit I, 248–9, 259–62.

³⁴ Ibid., 49–51, 129, 250–51.

³⁵ Ibid., 265–6.

³⁶ Ibid., 268–9; Pensées, 312–3.

³⁷ Considérations, 99–104.

³⁸ Ibid., 99; Vegetius, Epitome of Military Science, trans. N. P. Miller (Liverpool: Liverpool UP 1993), 54.

³⁹ Considérations, 90.

⁴⁰ Ibid., 236–7.

⁴¹ Réflexions, 345–6. Maurice of Nassau (1567–1625) and Coehon [Menno Van Coehorrn] (1641–1704) were notable Dutch authorities on siege warfare.

⁴² Lettres, 416, 419–20.

⁴³ For the implication that most wars are not resolved without multiple battles see Considérations, 185.

⁴⁴ Considérations, 235.

⁴⁵ L’esprit I, 276–305. Limitations of space prevent further consideration of this subject here.

⁴⁶ Ibid., 292–3.

⁴⁷ A brief account of the war can be found in Russell F. Weigley, The Age of Battles: The Quest for Decisive Warfare from Breitenfeld to Waterloo (Bloomington, IN: Indiana UP 1991), 105–16.

⁴⁸ L’esprit I, 293 with original emphasis.

⁴⁹ Considérations, 128.

⁵⁰ L’esprit, I, 295.

⁵¹ Gat 48, 50, 73-5.

⁵² Clausewitz, 175. See also Heuser, Strategy Before Clausewitz, 203, n12.

⁵³ Gat, 196.

⁵⁴ Ibid., 163–4, 196; Raymond Aron, Penser la guerre, Clausewitz, Volume 1: L’âge européen (Paris: Gallimard, 1976), esp. 24, 175, 295. Aron himself does not attach much significance to the possibility of Montesquieu’s influence over Clausewitz, although he maintains they shared common concerns in relation to ‘problems and methods’. Ibid., 374.

⁵⁵ This point comes through in Clausewitz, 966–71.

⁵⁶ In this respect see Clausewitz’s characterization of policy as ‘the intelligence of the personified state’. Ibid., 211–2.

⁵⁷ In this connection Montesquieu’s reference to the concept of friction is intriguing. ‘Mechanics certainly has its frictions that often change or arrest the effects of theory; politics likewise has its own’. L’esprit II, 138.

⁵⁸ Clausewitz, 212–3.

⁵⁹ Brinton et al., 91; Antoine-Henri Jomini, Précis de l’art de la guerre, ou nouveau tableau analytique des principales combinaisons de la stratégie, de la grande tactique et de la politique militaire, Vol. I (Paris: Libraire Pour l’Art Militaire, les Sciences et les Arts 1837), 157–8.

⁶⁰ Gat, 108, 128.

⁶¹ Jomini, Précis I, 5–23.

⁶² Ibid., 32–128.

⁶³ For an earlier synopsis of his narrower views see Antoine-Henri Jomini, ‘L’Art de la Guerre’, Pallas: Eine Zeitschrift für Staats- und Kriegs-Kunst, 1/1 (1808): 31–40.

⁶⁴ Antoine-Henri Jomini, Treatise on Grand Military Operations: or a Critical and Military History of the Wars of Frederick the Great, as Contrasted with the Modern System. Together with a Few of the Most Important Principles of the Art of War, trans. S. B. Holabird, Vol. II (New York: D. Van Nostrand 1865), 460–1. Gat (p. 128) reproduces substantially the same paragraph but omits the phrase ‘in his work upon the Causes of the Greatness and Decline of the Romans’.

⁶⁵ Antoine-Henri Jomini, Traité de grande tactique, ou relation de la guerre de sept ans, extraite de Tempelhof, commenté et comparée aux principales opérations de la dernière guerre; avec un recueil des maximes, justifiées par ces différents événements, 2 vols (Paris: Giguet et Michaud, Magimel 1805). The title was subsequently changed to Traité des grandes opérations militaires. Antoine-Henri Jomini, Traité des grandes opérations militaires, contenant l’histoire critique des campagnes de Frédéric II, comparées à celles de l’Empereur Napoléon; avec un recueil des principes généraux de l’art de la guerre, 2 vols, 2nd ed. (Paris: Magimel 1811).

⁶⁶ Jomini, Treatise II, 461–2.

⁶⁷ Jomini, Précis I, 74.

⁶⁸ Ibid., 143. Although Jomini might have read about the decline of Roman military performance directly in Vegetius, it was Montesquieu who connected this to the broader issue of imperial collapse.