The subject of rubber supply to the German and American war industries is not a topic which thus far has materialised in the context of the historiography on Hitler’s declaration of war on the US. Both countries were dependent on imports of this crucial product – the Germans to a lesser extent once their newly created synthetic rubber industry began to produce the new ‘Buna’ rubber in large quantities by 1939. At the time, well over 90 % of the world’s natural rubber came from plantations in Southeast Asia, with Malaya and the Dutch East Indies providing the bulk. This was a subject Hitler was thoroughly familiar with, not the least because his Auswärtiges Amt liaison official Walther Hewel had worked as a plantation manager in SE-Asia for several years.

American attempts to develop a synthetic rubber industry were stymied by a lack of clear government policy and a persistent refusal to believe that the fall of the East Indies to a Japanese invasion would be more than transitory. Hitler tended to see this problem in a different light: any Japanese move on this region would force the Americans into prematurely moving the bulk of their half-ready armed forces to contest such a move, thus diverting US attention away from Europe for a considerable time.