When Chamberlain agreed that war should be declared, he intended to meet any threat Hitler might offer in the air and to take any opportunities that might arise to sink such parts of the German navy as offered themselves to attack. There was no expectation of military victory and no real belief that the state of war need be turned into a war of steel and blood. Fortified by the neutrality of Italy and Japan and unimpressed by the Russo-German alliance, he believed that Hitler's bluff had been called. The French defences presented a deterrent in the West. Anglo-French effort could be directed at producing a collapse of the German home front as the German people came to understand that Hitler could not win.

Nor was this passive conception an aberration. The guarantee to Poland, so far from implying a will to fight, had been intended to make fighting unnecessary. Hitler had not been deterred, but he had had to ally himself with the Soviet Union.