Scapa Flow, flω', a sheltered body of water in Scotland's Orkney Islands. This stretch of sea, about 15 miles (24 km) long and 8 miles (13 km) wide, was a major British naval base in World Wars I and II. After the armistice in 1918 a large part of the German fleet, consisting of 77 surface vessels and 102 submarines, was interned at Scapa Flow by the victorious Allies. In June, 1919, caretaker German crews sank the vessels to prevent them from being divided among the Allied nations. In World War II, a German submarine penetrated British defenses at Scapa Flow in 1939 and sank the battleship Royal Oak.
Gallipoli Campaign, an Allied attempt in 1915, during World War I, to seize the Gallipoli Peninsula in Turkey and thus gain control of the Dardanelles strait, opening a supply route from the west to Russia through the Black Sea.
World War I was the great armed conflict of 191418. Until World War II, it was often called the Great War because it was the most destructive and widespread war the world had ever seen.