After the elections of 1933 Adolf Hitler took Germany in a radically different direction from where it had been headed after the Great War, the Treaty of Versailles and the short-lived Weimar Republic.
Besides sweeping constitutional changes and a rash of oppressive, race-based laws, Hitler was reorganising Germany in order for it to be ready for another major European project.
Russia and other European countries reacted in varying ways. In the meantime, other conflicts were brewing around the world, notably between China and Japan.
Here are 10 facts about the events that led to the full-on outbreak of the Second World War.
1. Nazi Germany engaged in a rapid process of rearmament through the 1930s
They forged alliances and psychologically prepared the nation for war.
2. Britain and France remained committed to appeasement
This was despite some internal dissent, in the face of increasingly inflammatory Nazi actions.
3. The Sino-Japanese war began in July 1937 with the Japanese invasion of Manchuria
This was carried out against a backdrop of international appeasement and is regarded by some as the start of World War Two.
4. The Nazi-Soviet Pact was signed on 23 August 1939
The Pact saw Germany and the USSR carve up central-eastern Europe between themselves and pave the way for German invasion of Poland.
5. The Nazi invasion of Poland on 1 September 1939 was the final straw for the British
Britain had guaranteed Polish sovereignty after Hitler flouted the Munich Agreement by annexing Czechoslovakia. They declared war on Germany on 3 September.
6. Neville Chamberlain declared war on Germany at 11:15 on 3 September 1939
Two days after their invasion of Poland, his speech was followed by what would become the familiar sound of air raid sirens.
7. Poland’s losses were overwhelming during the German invasion of September and October 1939
Polish losses included 70,000 men killed, 133,000 wounded and 700,000 taken prisoner in the defence of the nation against Germany.
In the other direction, 50,000 Poles died fighting the Soviets, of whom only 996 perished, following their invasion on 16 September. 45,000 ordinary Polish citizens were shot in cold blood during the initial German invasion.
8. British non-aggression at the start of the war was derided at home and abroad
We now know this as the Phoney War. The RAF dropped propaganda literature over Germany, which was humorously referred to as ‘Mein Pamph’.
9. Britain gained a morale-boosting victory in a naval engagement in Argentina on 17 December 1939
It saw the German battleship Admiral Graf Spee scuttled in the River Plate estuary. This was the only action of the war to reach South America.
10. The attempted Soviet invasion of Finland in November-December 1939 initially ended in comprehensive defeat
It also resulted in Soviet expulsion from the League of Nations. Eventually however the Finns were beaten into signing the Moscow Peace Treaty on 12 March 1940.