Second World War: HMS Curacoa (pictured) was accidentally rammed and sunk by RMS Queen Mary while escorting the liner to provide protection from submarine attacks.

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.

HMS Curacoa was a C-class light cruiser built for the Royal Navy during the First World War. She was one of the five ships of the Ceres sub-class and spent much of her career as a flagship. The ship was assigned to the Harwich Force during the war, but saw little action as she was completed less than a year before the war ended. Briefly assigned to the Atlantic Fleet in early 1919, Curacoa was deployed to the Baltic in May to support anti-Bolshevik forces during the British campaign in the Baltic during the Russian Civil War. Shortly thereafter the ship struck a naval mine and had to return home for repairs.

RMS Queen Mary is a retired British ocean liner that operated primarily on the North Atlantic Ocean from 1936 to 1967 for the Cunard Line. It is currently a hotel, museum, and convention space in Long Beach, California, United States. It is on the US National Register of Historic Places and member of Historic Hotels of America, the official program of the National Trust for Historic Preservation. Built by John Brown & Company in Clydebank, Scotland, she was subsequently joined by RMS Queen Elizabeth in Cunard's two-ship weekly express service between Southampton, Cherbourg and New York. These "Queens" were the British response to the express superliners built by German, Italian, and French companies in the late 1920s and early 1930s.