The neutrality of the United States had been seriously imperiled after the sinking of the Lusitania (1915). At the end of 1916, Germany, whose surface fleet had been bottled up since the indecisive battle of Jutland (see Jutland, battle of), announced that it would begin unrestricted submarine warfare in an effort to break British control of the seas. In protest the United States broke off relations with Germany (Feb., 1917), and on Apr. 6 it entered the war. American participation meant that the Allies now had at their command almost unlimited industrial and manpower resources, which were to be decisive in winning the war. It also served from the start to lift Allied morale, and the insistence of President Woodrow Wilson on a "war to make the world safe for democracy" was to weaken the Central Powers by encouraging revolutionary groups at home.
The war on the Western Front continued to be bloody and stalemated. But in the Middle East the British, who had stopped a Turkish drive on the Suez Canal, proceeded to destroy the Ottoman Empire; T. E. Lawrence stirred the Arabs to revolt, Baghdad fell (Mar., 1917), and Field Marshal Allenby took Jerusalem (Dec., 1917). The first troops of the American Expeditionary Forces (AEF), commanded by General Pershing, landed in France in June, 1917, and were rushed to the Château-Thierry area to help stem a new German offensive.
A unified Allied command in the West was created in Apr., 1918. It was headed by Marshal Foch, but under him the national commanders (Sir Douglas Haig for Britain, King Albert I for Belgium, and General Pershing for the United States) retained considerable authority. The Central Powers, however, had gained new strength through the Treaty of Brest-Litovsk (Mar., 1918) with Russia. The resources of Ukraine seemed at their disposal, enabling them to balance to some extent the effects of the Allied blockade; most important, their forces could now be concentrated on the Western Front.
The critical German counteroffensive, known as the second battle of the Marne, was stopped just short of Paris (July–Aug., 1918). At this point Foch ordered a general counterattack that soon pushed the Germans back to their initial line (the so-called Hindenburg Line). The Allied push continued, with the British advancing in the north and the Americans attacking through the Argonne region of France. While the Germans were thus losing their forces on the Western Front, Bulgaria, invaded by the Allies under General Franchet d'Esperey, capitulated on Sept. 30, and Turkey concluded an armistice on Oct. 30. Austria-Hungary, in the process of disintegration, surrendered on Nov. 4 after the Italian victory at Vittorio Veneto.
German resources were exhausted and German morale had collapsed. President Wilson's Fourteen Points were accepted by the new German chancellor, Maximilian, prince of Baden, as the basis of peace negotiations, but it was only after revolution had broken out in Germany that the armistice was at last signed (Nov. 11) at Compiègne. Germany was to evacuate its troops immediately from all territory W of the Rhine, and the Treaty of Brest-Litovsk was declared void. The war ended without a single truly decisive battle having been fought, and Germany lost the war while its troops were still occupying territory from France to Crimea. This paradox became important in subsequent German history, when nationalists and militarists sought to blame the defeat on traitors on the home front rather than on the utter exhaustion of the German war machine and war economy.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.