World War II: Japanese forces invade Christmas Island, then a British possession.

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 Battle of Christmas Island was a small engagement which began on 31 March 1942, during World War II. Assisted by a mutiny of soldiers of the British Indian Army against their British officers, Imperial Japanese Army troops were able to occupy Christmas Island without any land-based resistance. The United States Navy submarine Seawolf caused severe damage to the Imperial Japanese Navy cruiser Naka during the landings.