Abstract
This article examines the efforts of French and British intelligence services to assess the German economy before and during the opening stage of World War II. The French and British, attached to a long‐war strategy based on the assumption time worked in their favour, looked to economic intelligence to indicate whether this was in fact the case. Yet for a variety of reasons clear and consistent assessments were impossible. Rather than accept uncertainty, the French and British chose to impose certainty by assuming the worst, a decision which contributed to the abandonment of a long‐war strategy as the Allies began to search for some way to win a short war.