World War II: The Polish government of Ignacy Mościcki flees to Romania.

World War II or the Second World War was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks and aircraft played major roles, enabling the strategic bombing of cities and delivery of the first and only nuclear weapons ever used in war. World War II is the deadliest conflict in history, causing the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.

Ignacy Mościcki was a Polish chemist and politician who was the country's president from 1926 to 1939. He was the longest serving president in Polish history. Mościcki was the President of Poland when Germany invaded the country on 1 September 1939 and started World War II.