Second World War: The German submarine U-47 torpedoed and sank the Royal Navy battleship HMS Royal Oak while the latter was anchored at Scapa Flow in Orkney, Scotland.

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.

German submarine U-47 was a Type VIIB U-boat of Nazi Germany's Kriegsmarine during World War II. She was laid down on 25 February 1937 at Friedrich Krupp Germaniawerft in Kiel as yard number 582 and went into service on 17 December 1938 under the command of Günther Prien.

The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against France. The modern Royal Navy traces its origins to the English Navy of the early 16th century; the oldest of the UK's armed services, it is consequently known as the Senior Service.

HMS Royal Oak was one of five Revenge-class battleships built for the Royal Navy during the First World War. Completed in 1916, the ship first saw combat at the Battle of Jutland as part of the Grand Fleet. In peacetime, she served in the Atlantic, Home and Mediterranean fleets, more than once coming under accidental attack. Royal Oak drew worldwide attention in 1928 when her senior officers were controversially court-martialled, an event that brought considerable embarrassment to what was then the world's largest navy. Attempts to modernise Royal Oak throughout her 25-year career could not fix her fundamental lack of speed and, by the start of the Second World War, she was no longer suitable for front-line duty.