Name generally given to the set of military conflicts during the years 1914–1918 that set the armies of Germany, Austria-Hungary, Turkey, and Bulgaria (the Central Powers) against those of Great Britain, France, Russia, Italy, the United States, and other countries (the Allied and Associated Powers, more commonly known as the Allies or the Entente). The geographical scope of the war, the sophistication of weapons employed by both sides, the human cost of the fighting among both soldiers and civilian populations—all of these were at the time unprecedented in the history of warfare, and during the subsequent two decades the experience of the war weighed heavily upon the thinking and behavior not only of political leaders but of virtually all who had been affected by it.
