The Final Descent into War: Aggression, Alliances & the Crisis of 1939

Germany and the USSR — bitter ideological enemies — signed the Nazi-Soviet Pact in August 1939 because, for very different reasons, the deal suited both at that moment.

The most important reason for Hitler was to avoid a two-front war. Germany's defeat in 1918 had been shaped by fighting on two fronts, and Hitler was determined not to repeat it. By neutralising the USSR with a non-aggression pact, he freed himself to invade Poland without fear of Soviet intervention. The pact removed the last major obstacle to attacking Poland, which he intended to do within weeks.

For Stalin, the key motive was to buy time. The Red Army had been gravely weakened by Stalin's purges of its officers, and the USSR was not ready for a war with Germany. The pact bought breathing space to rearm. Stalin also distrusted Britain and France, whose talks with Moscow had been half-hearted and who had already abandoned Czechoslovakia at Munich.

Finally, both sides gained from the secret protocol, which divided Poland and Eastern Europe into spheres of influence. This offered Stalin territory (eastern Poland and the Baltic) and a buffer zone, while giving Hitler a free hand in the west of Poland. Each leader privately expected to betray the other, but in August 1939 the cynical bargain served both — and made the invasion of Poland possible.

Britain and France guaranteed Poland's independence in March 1939 mainly because Hitler's seizure of the rest of Czechoslovakia had finally destroyed their faith in appeasement and convinced them that he had to be stopped.

The decisive reason was the occupation of Prague. At Munich in 1938, Chamberlain had accepted Hitler's claim that he only wanted German-speaking territory. When German troops took the rest of Czechoslovakia in March 1939 — land with no German-speaking justification — it shattered that claim and proved Hitler's ambitions were unlimited. Appeasement had clearly failed.

A second reason was the need to deter further aggression. With Czechoslovakia gone, Poland looked like the obvious next target because of German demands over Danzig and the Corridor. By publicly guaranteeing Poland, Britain and France hoped to draw a line and warn Hitler that the next act of aggression would mean war, rather than another negotiated surrender.

Finally, there was strong public and political pressure to abandon appeasement. Outrage at the broken Munich promise made a tougher stance politically necessary. The guarantee therefore marked the end of appeasement and signalled that Britain and France were now prepared to fight, which is exactly what happened when Germany invaded Poland in September.

Similarity. Both sources agree that Hitler was determined and aggressive, and that his ambitions reached beyond simply uniting German-speakers. Source A describes 'a calculated bid for the domination of Europe by force', while Source B reports that the Fuhrer was set on action over Poland and willing to take great risks ('he gambles too far'). Both therefore present a Hitler resolved to expand and to use the threat of war to do so.

Difference. The sources disagree about WHAT Hitler intended to achieve. Source A presents him as deliberately seeking a general war for the 'domination of Europe' — a planned bid for mastery. Source B, by contrast, suggests Hitler did not expect a general war at all: he believed 'the British will bluster but not fight, as they did over the Czechs', and was preparing 'for Poland alone'. Where A sees calculated aggression aimed at conquering Europe, B sees a gamble based on the assumption that the Allies would back down again.

Explaining the difference (provenance and context). The contrast is best explained by who produced each source and why. Source A is a public speech by a British politician (March 1939), made just after the seizure of Prague to rally opinion against Hitler and justify a tougher stance; it naturally portrays Hitler in the worst possible light as a deliberate aggressor. Source B is a private German military diary (August 1939) never meant for publication, so the general can record his genuine, anxious belief that Hitler was miscalculating. The different natures and purposes explain why one stresses a master-plan and the other a risky gamble — and together they capture the real historical debate over whether Hitler planned war or merely expected another bloodless triumph.

The failure of appeasement was certainly an important reason war broke out in 1939, but it worked alongside Hitler's own aims and the Nazi-Soviet Pact, and it is argued here that appeasement's collapse shaped the TIMING of war while Hitler's expansionism was the deeper cause.

The case for appeasement's failure. For years Britain and France gave way to Hitler — over the Rhineland (1936), the Anschluss (1938) and the Sudetenland at Munich (1938). Each surrender emboldened him to gamble again. When Hitler seized the rest of Czechoslovakia in March 1939, the policy was exposed as a failure, forcing Britain and France to reverse course and guarantee Poland. It was this hardening — the refusal to appease again — that turned the invasion of Poland into a general war. Without the failure and abandonment of appeasement, Hitler might have expected yet another bloodless triumph.

The case for other factors. However, appeasement did not create Hitler's ambitions. His aim of Lebensraum meant eastward expansion, and so war with Poland and Russia, was always likely at some point regardless of British policy. The Nazi-Soviet Pact of August 1939 was decisive in the short term: by neutralising the USSR it removed the last barrier and made invasion possible precisely in 1939. Unresolved Versailles grievances (Danzig and the Corridor) supplied the specific flashpoint. War therefore had causes far beyond appeasement.

Judgement. If 'main reason' means the factor that determined WHY war came in 1939 rather than earlier or later, then the failure of appeasement and the Nazi-Soviet Pact were decisive for the timing — the first by forcing a stand over Poland, the second by clearing the path. But the underlying driver was Hitler's expansionist aims, without which there would have been no aggression to appease in the first place. Appeasement's failure was thus a crucial proximate cause, but not the deepest one.

Hitler was the most responsible single figure for the outbreak of war in 1939, but his responsibility must be weighed against the failures of others — appeasement and the League — and the structural legacy of Versailles. This answer judges 'most responsible' as the factor without which war would not have come in 1939, and engages directly with the historiographical debate between the intentionalist view of Hitler-the-planner and A.J.P. Taylor's view of Hitler-the-opportunist.

The case for Hitler's responsibility (the intentionalist view). Hitler's foreign-policy aims drove events. His ambition for Lebensraum in the east made a war of conquest against Poland and the USSR almost inevitable at some point, and the Hossbach Memorandum (1937) is often read as evidence of long-laid plans. The decisive proof of unlimited ambition was the seizure of Prague in March 1939 — territory with no German-speaking justification, which exposed every earlier 'reasonable' demand as a stepping-stone. It was Hitler who built the Nazi-Soviet Pact to clear the path and who ordered the invasion of Poland. On this reading, war came because Hitler willed expansion.

The case for other factors (the structuralist view). Yet Taylor argued Hitler was an opportunist who exploited the blunders of others rather than following a fixed timetable. The failure of appeasement repeatedly rewarded aggression — the Rhineland, the Anschluss, Munich — teaching Hitler that the Allies would not fight, so that in 1939 he may have gambled they would back down again rather than seeking a general war. The weakness of the League of Nations had already failed to deter aggression elsewhere. And the resentments left by Versailles — Danzig and the Corridor — created the very grievances Hitler could exploit. War, on this view, was as much the product of others' mistakes as of one man's plan.

Judgement. Hitler was the prime mover: his aims supplied the ambition, and no other figure was driving expansion. But the failure of appeasement and the League removed the restraints that might have stopped him, and Versailles supplied the grievances. The most convincing verdict is that Hitler's expansionist aims made a war of eastern conquest highly likely eventually, while the collapse of appeasement and the Nazi-Soviet Pact determined that it broke out precisely in 1939. Hitler bears the primary responsibility, but he succeeded only because others failed to resist him in time.

The sources offer real support for the view that Hitler intended aggressive expansion, but they are sharply divided over whether he PLANNED a general war in 1939, with some pointing instead to a gamble and to the failures of others.

Sources that support the view (Hitler planned war). Sources A and C provide the clearest support. Source A, a politician's speech after Prague, presents Hitler's actions as 'a calculated bid for the domination of Europe by force' — deliberate, planned aggression. Source C reinforces this by citing the Hossbach Memorandum as evidence that Hitler had outlined 'a programme of conquest' to his commanders as early as 1937. Cross-referenced, A and C agree that war flowed from a long-held intention to dominate Europe by force.

Sources that challenge the view. Sources B and D qualify this picture. Source B, a German general's private diary, suggests Hitler did NOT expect a general war: he believed the British would 'bluster but not fight' and prepared 'for Poland alone' — implying a gamble, not a master-plan for European war. Source D shifts responsibility away from Hitler's planning altogether, blaming 'our own years of weakness and retreat' (appeasement) for convincing Hitler he could act with impunity. Together they support the structuralist case that war owed much to miscalculation and to the mistakes of others.

Evaluation of the sources. Provenance affects how much weight each carries. Source A is a public speech designed to rally opinion against Hitler, so it has good reason to portray him in the worst light as a deliberate planner — useful for British attitudes but not a neutral verdict. Source C is a post-war prosecution document (1946), which had a clear interest in proving German guilt and may read more design into the Hossbach Memorandum than it strictly proves. By contrast, Source B is a private diary never meant for publication, so it is candid evidence of genuine military doubt, and Source D, a private memo, can frankly admit British failings it would not state publicly. The most candid sources (B and D) are precisely the ones that question a planned general war.

Judgement on 'how far'. The sources strongly support the view that Hitler intended aggressive EXPANSION (A and C), but they support the narrower claim that he planned a GENERAL WAR in 1939 only to a limited extent. The two most reliable sources — the candid diary (B) and the private memo (D) — suggest Hitler gambled that the Allies would not fight, and that appeasement had encouraged him. Taken together, the sources support the view that Hitler willed expansion and risked war, rather than that he deliberately planned a general European war in 1939: aggression, yes; a calculated general war, only partly.