When a German warship opened fire on the Polish garrison in the special area reserved for them within the Free City of Gdansk (Danzig)—and German troops and airplanes attacked Poland—a terrible conflict began that was quickly called “The Second World War.” This name implies some relationship to the great prior conflict of 1914-18. At the beginning of September 1939, when German actions started this new war, however, there was already fighting in two other areas of the globe. Since the Japanese had struck in northern China in July 1937, there had been hostilities between the two East Asian nations; that war had reached something of a stalemate by the fall of 1939, but no end to it was in sight. In addition, since May 1939, Japanese and Russian troops were engaged in bitter fighting on the border of their respective puppet states in a conflict called after its location the Nomonhan Incident by the Japanese and the Khalkhin-gol Incident by the Russians. Diplomatic relations between the Soviet Union and Japan continued even while their forces clashed, and a cease-fire in this struggle on September 16, 1939, followed upon Japan's defeat in battle. The continuing East Asian conflict between Japan and China would, however, have remained isolated, like the war those two nations had fought in 1894-95, had not events in Europe led Japan to join the hostilities begun there. It is thus entirely appropriate to think of the Second World War as having been initiated by Germany and eventually embroiling the whole globe. How did this come about? Was not one world war enough?

The war which ended with the armistice of November 11, 1918, had been horrendous in its impact on the participants. In more than four years of bloodshed and destruction, vast portions of Europe had been wrecked and the domestic institutions of the continent transformed. The capacity of the modern state for mass mobilization had drawn human and material resources out of each belligerent to an extent no one had previously imagined possible, and these human and material resources had been consumed in the furnace of war.