At first glance, the Battle of the Atlantic appears to be the arena of war most likely to provide a trigger for a German declaration of war on the USA. The US Navy had been establishing a presence in the eastern half of the North Atlantic with increasing assertiveness since April 1941 and even began escorting British convoys in mid-September 1941. Historians attempting to integrate these events into Hitler’s decision to declare war on the US fall into two different camps. One see in it an unavoidable reaction to the presence of US escorts who were stymying the efforts of his U-boats to get at the convoys, while other maintain the he was longing to unleash his submersibles at the vulnerable merchant traffic in US waters.

I am now in a position to prove that neither was the case. US escorts only rarely had to prove their worth, because of the low number of convoy interceptions between July-December 1941 – a direct consequence of the rerouting of convoys thanks to the work done in Bletchley Park. Also, not a shred of evidence exists to suggest that either Raeder or Dönitz regarded patrols to the Americas as a missed opportunity.

On 3 January 1942 Ambassador Oshima paid his second house call on the German dictator in fewer than three weeks. Hitler’s fondness for the Japanese envoy notwithstanding, such a minimal gap between two visits was unheard of and could only be justified by the need to brief the new Far Eastern ally on some unforeseen event. As was to be expected, much of the time the two men spent in conference was an attempt by the dictator to cover up the near-collapse of the German frontline outside Moscow. Hitler may have held the Japanese diplomat in high regard, but he still resorted to bare-faced lying to counter any rumours about the Ostheer’s crisis that may have reached the Japanese embassy.

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.

Conventional wisdom has it that on the day of Hitler’s declaration of war on the US, the Ostheer was reeling under the blows of a massive Soviet counteroffensive unleashed on December 5th, 1941 and which should have put paid to any notions of demobilising just a part of the army to free up labour for shipyards and the aeronautical industry. A closer examination of the primary sources, however, reveals that the Soviet counterstrike developed in such a gradual and haphazard fashion that a sense of alarm only began to develop in the days after December 13th and did not reach crisis point until December 18th. A number of different factors – to be discussed in detail in the chapter – favoured this dynamic.

Allied lend-Lease shipments to the USSR were carefully recorded, but not regarded as a threat because it was felt that the losses of the 1941 campaign season and the loss of the Donbass had crippled the regenerative powers of the Red Army to such an extent that a comeback was no longer feasible. Belated attempts to coordinate a global strategy with Japan in late December indicates that it was around this time that this estimate was reassessed.

The declaration of war on the US found a Luftwaffe which was already stretched to the limit. 80 % of its units were supporting the war in Russia, with the remainder engaged in western Europe and N. Africa. In Germany the Flak arm (anti-aircraft units were part of the Luftwaffe) was engaged in checking the initial phase of Bomber Command’s war against German cities. Against such a backdrop, a further escalation of the war would appear to be a suicidal undertaking. This chapter will focus on how Hitler and Luftwaffe C-in-C Göring would have perceived the situation in November/December 1941. All available sources support the idea that Hitler had every reason to take an optimistic view of the future development of the air war. Three new promising aircraft designs were nearing readiness, recent victories in Russia led to the shift of a substantial number of units to the Mediterranean and Bomber Command’s campaign against German urban areas had been checked by the introduction of a gun-laying radar for the Flak arm. A series of unexpected events which occurred from late December 1941 would reveal these expectations to be false hopes, but this fact would have remained hidden from the German leadership in early December.

The output of large parts of the German war economy was, if not quite in crisis, then certainly lagging by the autumn of 1941. It had reached a point where it was struggling to meet the current demands of the field army in Russia fighting in Russia, let alone those raised by the planned large-scale expansion of the Luftwaffe. Against such a backdrop, the idea of escalating the war by dragging another great power into it gives legitimacy to the view put forward by some historians that Hitler was seeking his self-immolation.

A close examination of the sources, however, indicates that Hitler had reached the conclusion that far from having hit a glass ceiling the German economy still possessed considerable slack which could be mobilised by rationalising designs and optimising the allocation of labour and raw materials. As a precedent, he could point to the months of January-April 1940 where a last-minute spurt in productivity had provided much of the ammunition and tanks needed for the campaign in the West. It goes without saying that this forecast mistakenly assumed a marked decrease in the intensity of the fighting in Russia on account of the fall of the Donbass industrial area.

The introduction will attempt to give an overview of the existing scholarship on the topic of what can safely be regarded as Hitler’s most idiosyncratic and poorly understood decision: his declaration of war on the USA in December 1941. No monograph exists on the subject: those historians who have engaged with it have done so in the context of articles, general histories of WW 2 and biographies of either Hitler or Roosevelt. It is often described as an impossible-to-fathom irrational decision and this may well be the reason why quite a few authors have decided to omit any mention of it in their books.

Two main schools of thought can be said to exist: the one initiated by Andreas Hillgruber (1925-1989) maintains that the dictator, when faced with the prospect of military defeat in November 1941 chose to declare war on the US as a gesture to mask the fact that he had lost the initiative or indeed was seeking self-immolation. Eberhard Jäckel (1929-2017) and his followers insist that he was hoping to force the US to split its resources between two oceanic theatres. It is my considered opinion that both theories raise more questions than they answer and will propose a new one.

Ever since Ellen Gibbels’ research proved that Hitler was suffering from Parkinson’s Disease, historians have been asking themselves the question whether the progress of the illness is likely to have affected his judgement by 1944/45. Far more relevant is the as yet unaddressed question whether he could have known of his condition in time to influence his decision to throw down the gauntlet to the USA. This should not be seen as a far-fetched notion, since the dictator is on record as repeatedly tying the rise and fall of Germany as a great power to his life span; hence, the realisation that he was afflicted with a mortal and debilitating disease might indeed have driven him into a strategy best described as suicidal (as many historians have indeed chosen to label this decision, without one of them, however tying it to a possible diagnosis of Parkinson’s). The surviving notes taken by his personal physician Theodor Morell, together with other sources, prove conclusively that while the first symptoms of Parkinson’s may have manifested themselves before December 11th, 1941 he did not receive a diagnosis to this end before April 1945. His decisionmaking in December 1941 was as yet unaffected by his medical condition.

While virtually all the historians who have discussed the reasons behind Hitler’s decision to declare war on the US agree that he was resigned to an imminent entry of the US into WW 2, so far no one has made a plausible case for one particular political or military move by Washington tipping him over the edge. From the “Destroyers-for-Bases” deal of September 1940 to the de-facto abolition of the 1939 Neutrality Law an already pro-Allied Roosevelt administration got progressively more and more involved in the war against Nazi Germany while still claiming the status of a neutral. Assessing which of these steps was decisive in predisposing the German leader towards a declaration of war is a major challenge, since no document for internal consumption summarising his thoughts on the matter has ever emerged.

A detailed examination of military and diplomatic records, together with his acolytes’ personal diaries indicates that it was the passing of the legislation which gutted the US Neutrality Law (November 13th) which is most likely to have put him in a frame of mind where war with the US was seen as something inevitable, since this guaranteed the imminent arrival of US civilian shipping in the NW approaches of the UK.

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.