Chapter 28 : World War I In the late 1800s, nationalism and imperialism led the nations of Europe to form two rival alliances: the Triple Alliance, made up of Germany, Austria-Hungary, and Italy; and the Triple Entente (later the Allies), consisting of France, Great Britain, and Russia. Conflict broke out between the two alliances in 1914, and the belligerents fought for four years, using trench warfare and such new weapons as machine guns, tanks, airplanes, and poison gas. The war quickly settled into a stalemate with neither side able to win a quick, total victory. To end a blockade of their ports, German U-boats attacked American merchant ships. Thus drawn into the war, the United States support made the necessary difference, and in 1918 the Germans finally surrendered to the Allies. A parallel conflict took place in 1917 as Russian working people and soldiers upset the czarist system and took over the government. The war caused great human misery; millions of soldiers and civilians died or were wounded.