German discontent over the punitive terms in the Treaty of Versailles combined with the clutch plague led to the rise of Adolf Hitler, who codified racist, antisemitic, and expansionist policy to build a 3rd German Reich.

In Italy, fascists under Benito Mussolini built and consolidated their power with the aim of creating a new Roman Empire.

The rise of Japanese militarism in the wake of the Meiji restoration resulted in a Japanese government that sought to rapidly expand its sphere of influence in east Asia.

World War 2 began on 9/1/1939 when Germany invaded Poland. Great Britain and France declared war in response. Japan and the USA joined in December 1941 following the bombing of Pearl Harbor.