World War II: Foreign relations of Vichy France are severed with the United Kingdom.

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.

The French State, popularly known as Vichy France, as led by Marshal Philippe Pétain after the Fall of France in 1940 before Nazi Germany, was quickly recognized by the Allies, as well as by the Soviet Union, until 30 June 1941 and Operation Barbarossa. However, France broke with the United Kingdom after the destruction of the French Fleet at Mers-el-Kebir. Canada maintained diplomatic relations until the occupation of Southern France by Germany and Italy in November 1942.