In 1914, the automaticity of alliances led to conflagration; in 1939, the opposite was true. The alliance system was so weak (or cowardly?) that it had no deterrent virtue. The führer was therefore able to methodically play his tricks, from the remilitarization of the Rhineland (1936) to the invasion of Czechoslovakia (March 15, 1939). He then took the risk of aggressing against Poland, counting on its allies' abstention. "Our enemies are little worms. I saw them at Munich," he told his military chiefs. The declaration of war from London and then Paris therefore came as a surprise, since the Reich was banking on a limited conflict. For although Article 5 of the treaty obliges the signatories to react, it does not postulate the use of cannons: The parties must only take actions deemed necessary, "including the use of armed force." In short, the use of weapons is merely one option left to the free judgment of states. The war went global in 1941, not because o...