World War II: The Luftwaffe conducted a surprise air raid on Allied ships in Bari, Italy, sinking twenty-eight vessels and releasing one ship's secret cargo of mustard gas.

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 Luftwaffe was the aerial-warfare branch of the Wehrmacht before and during World War II. Germany's military air arms during World War I, the Luftstreitkräfte of the Imperial Army and the Marine-Fliegerabteilung of the Imperial Navy, had been disbanded in May 1920 in accordance with the terms of the 1919 Treaty of Versailles, which banned Germany from having any air force.

The air raid on Bari was an air attack by German bombers on Allied forces and shipping in Bari, Italy, on 2 December 1943, during World War II. 105 German Junkers Ju 88 bombers of Luftflotte 2 surprised the port's defenders and bombed shipping and personnel operating in support of the Allied Italian Campaign, sinking 27 cargo and transport ships, as well as a schooner, in Bari harbour.

The Allies, formally referred to as the United Nations from 1942, were an international military coalition formed during World War II (1939–1945) to oppose the Axis powers. Its principal members were the "Big Four" – the United Kingdom, United States, Soviet Union, and China.