After four years of fighting, World War 1 ends. The victorious nations assemble at Versailles to design the peace that they will impose on the defeated - Germany and Austria-Hungary.
The Peacemakers have gone home. America has rejected its President's peace settlement and withdrawn into its previous isolationist position. Meanwhile, Europe wrestles with its debt.
Prohibition doesn't stop anyone from having a good time. The U.S. is on wheels or listening to the radio, welcoming the talkies or investing in the stock market with reckless optimism.
What had seemed to be an economic recovery is revealed to have been at best fragile, and the world enters a global depression of unprecedented and unmeasurable savagery.
In different ways, in different places, new leaders take centre stage. Hitler in Germany, Roosevelt in the United States. Militarism triumphs in Japan, which consolidates its invasion of China's north east.
In the Union of Soviet Socialist Republic's repression, gulags, collectivisation, and Five-Year plans are beginning to tally the human toll that will always be associated with Stalin's rule.
The power in Europe has finally and fatally shifted - the resurgent Germany of the Third Reich is the dominant force. War rips Spain apart as a three year civil war of terrible brutality starts.
Little more than 20 years after the guns fell silent, they roar back into life. Hitler annexes all of Czechoslovakia. Britain and France respond with promises to Poland.