Nazi-Soviet Pact, Poland and the Outbreak of War
A Diplomatic Revolution
For most of the 1930s, Hitler and Stalin had presented one another as ideological enemies. Nazism rested on militant anti-communism; the Soviet Union had built the Comintern to fight fascism. The Anti-Comintern Pact of 1936 had been openly aimed at Moscow. So when, on the night of 23 August 1939, Joachim von Ribbentrop and Vyacheslav Molotov signed a non-aggression pact in the Kremlin, the world was stunned. The Nazi-Soviet Pact reversed every assumption of European diplomacy. It is one of the clearest examples of a diplomatic revolution in twentieth-century history.
August-September 1939 saw four hinge events: Anglo-French-Soviet talks failed in mid-August; the Nazi-Soviet Pact was signed on 23 August; Germany invaded Poland on 1 September; Britain and France declared war on 3 September. Soviet forces entered eastern Poland on 17 September.
Why Stalin Signed
Stalin’s motives were practical, not ideological. Soviet diplomacy through summer 1939 had pursued two tracks at once. From April, Britain and France had been negotiating a tripartite alliance with Moscow against further German aggression. The talks dragged. Britain sent only a junior delegation by the slowest route. The Western powers refused to put pressure on Poland to permit Soviet troops to cross Polish territory in any future war — meaning the Red Army could not actually fight Germany on the eastern front. Stalin concluded the British and French were not serious. Meanwhile Hitler, who needed an eastern flank secured before invading Poland, offered Stalin terms the Western powers could not match: a non-aggression pact, territorial gains in eastern Europe, and time. The deal was signed on 23 August 1939.
A secret protocol divided eastern Europe into spheres of influence. Germany would take western Poland; the USSR would take eastern Poland, Estonia, Latvia, Finland and Bessarabia (later modified to include Lithuania). The protocol was hidden from the public; it remained denied by Moscow until 1989.
Britain and France had genuine reasons to hesitate. The British political class distrusted Stalin’s purges, his record on collectivisation, and the Comintern’s role in fomenting communist movements abroad. The Polish government, with bitter memories of the 1920 Soviet-Polish War, refused to allow Soviet troops on Polish soil. Yet the slowness was striking: the British naval mission to Moscow took five days by passenger ship while Ribbentrop flew to Moscow in a single afternoon. Stalin’s judgement that the West was buying time, not seriously seeking an alliance, was not unreasonable. Historians remain divided on whether a serious British effort in spring 1939 could have produced a different outcome.
1 September: Poland
With his eastern flank secured, Hitler launched the invasion of Poland at 4:45 a.m. on 1 September 1939. The German armed forces deployed the new Blitzkrieg tactics — armoured columns supported by close air support and motorised infantry — that would later overrun France. The Polish army, although large, was poorly equipped to face this combination. Britain and France issued an ultimatum demanding immediate withdrawal. Hitler ignored it. On 3 September 1939, Britain and France declared war.
On 17 September 1939, Soviet forces invaded eastern Poland from the east, in line with the secret protocol. By the end of September, Poland had ceased to exist as a state. Britain and France had honoured their guarantee, but they had no realistic way of helping Poland militarily; the Anglo-French expectation was that the war would be long and decided in the west.
Responsibility for the War
Responsibility for the outbreak of war is usually weighed among Hitler, Stalin and Chamberlain. There is no single answer; the strongest responses present these as competing arguments rather than picking one and ignoring the others.
Hitler is the prime mover. Every territorial action between 1933 and 1939 had been a German one: leaving the League, rearmament, the Rhineland, Anschluss, the Sudetenland, Prague, Danzig. The historian A.J.P. Taylor controversially argued in The Origins of the Second World War (1961) that Hitler was an opportunist exploiting circumstances rather than a master planner executing a step-by-step programme. Most modern historians sit between Taylor and the older ‘intentionalist’ view: Hitler was both opportunist and planner. The 1939 invasion of Poland was a deliberate German choice.
Stalin is an opportunist. The Nazi-Soviet Pact removed the eastern obstacle that might have deterred Hitler. Stalin gained territory in eastern Poland, the Baltic states and Bessarabia, and bought time to build up the Red Army. The pact made the September invasion possible in its actual form — Hitler would not have moved without it. Stalin shares responsibility for enabling the immediate trigger, but did not start the war.
Chamberlain represents the failure of British policy. The wartime ‘Guilty Men’ tradition (Cato, 1940) blamed appeasement for emboldening Hitler. The revisionist tradition (Reynolds, McDonough) stresses that he faced real constraints and bought time for British rearmament. Most modern historians treat appeasement as a rational response to those constraints that nonetheless made costly errors — especially Munich, the abandonment of Czechoslovakia, and the slowness of the 1939 Moscow negotiations.
The historiographical debate over Hitler’s 1933-39 foreign policy is between ‘intentionalists’ (Hitler had a master plan from Mein Kampf onwards) and ‘structuralists’ (Hitler was an opportunist exploiting circumstances). A.J.P. Taylor was the first major historian to argue the structuralist case. Most modern historians draw on both traditions: the broad goals (treaty revision, pan-Germanism, Lebensraum) were consistent, but the particular moves and the timing reflected opportunity. Present the debate as competing interpretations rather than picking one and ignoring the other.
Responsibility for war can be weighed across three figures. Hitler was the prime mover — every territorial action 1933-39 was German. Stalin was an opportunist who enabled the trigger via the Nazi-Soviet Pact. Chamberlain represents the failure of appeasement, though historians remain divided on whether his policy was rational or cowardly.