Somme, Battle of the, was one of the longest and costliest campaigns of World War I (1914-1918). It took place in northern France during the summer and autumn of 1916 and consisted of a series of largely unsuccessful offenses by British and French troops against part of Germany's western battlefront. The Battle of the Somme was one of the bloodiest and most futile examples of trench warfare in history. See World War I.