The outbreak of WW1: a contribution of rational decision making

Alain Trannoy (EHESS/AMSE)

February 12, 2019, 12:45–13:45


Room MF 323

IAST Lunch Seminar


We build a decision model enabling to predict the choice between war and peace. This model articulates root causes as the risk of future war and other contingent factors such as the potential gains/losses in case of victory/defeat and the potential losses linked to the war itself. We calibrate the model to the case of British, French, German, Russian, decision-makers at the end of July 14, taking into account the decisions already taken by the Austrian Hungarian Empire. We consider the case of a short war that would not have gone beyond the end of 1914. Our model predicts that France and Germany went to war, the preventive-war argument (doing war today is better than tomorrow) prevailing for both countries, with for France the additional benefits linked to the return of Alsace-Moselle to France in case of victory. For the Russian and British Empires, the case for seizing war was more dubious. The calibration reveals that when asked which of the two countries, France and Germany, seemed to have the most interest to war, France emerges as the best candidate, enabling to explain the passive behavior of French decision-makers, Raymond Poincaré ahead, who, if they did not aim at war, did not do their best to avoid it. Beyond, the timing of decisions of Entente’s partners, who did not coordinate, represents a major factor of the outbreak of war on July 14.