Japan began to play a major part in Hitler’s calculations after Italy’s spate of military disasters from November/December had made it clear that Mussolini’s military were turning from asset to liability. From that point onwards, considerable diplomatic leverage was invested into goading the Japanese into joining the war against the UK (January-June 1941) and then, the USSR (July-October 1941). At the same time, German representatives consistently urged the Japanese not to bring the Americans into the war. Bilateral relations between the two would-be allies were far from harmonious, however. Some Japanese spokesmen would make quite specific promises about the imminent participation of Tokyo in the war, while others kept insisting on further German military successes before they would consider making the jump. The pro-German foreign secretary Matsuoka was sacked in July and between May and September 1941, US-Japanese negotiations appeared to presage a détente between both countries and Tokyo’s withdrawal from the Tripartite Pact.

It is against this background that in mid-November a renewed Japanese commitment to enter the war produced a breakthrough. Japanese insistence to extend hostilities to the US might could have turned into a hindrance, but the coincidental abolition of the US Neutrality Law had prepared the ground for US-German hostilities.