The war begins. Attacking in Poland after signing a non-aggression Pact with the Soviet Union, German and Soviet troops divide the country. World War II begins when the British and French declare war. In China, the Sino-Japanese War reignited in 1937 after low-intensity conflicts since the Mukden Railroad incident in 1931.
World War 2 - Timelines
1939 - Wikipedia, the free encyclopedia
The 1939-40 New York World’s Fair
The Avalon Project : Nazi-Soviet Relations 1939-1941