The sinking of the Lusitania was one of the events that brought the United States into World War I. The topics in this section cover some of the major concepts and events related to the start of the First World War.

Lausanne Conference

Lausanne Conference, 1922-23, an international meeting held at Lausanne, Switzerland, from November, 1922, to July, 1923.

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  • Europe After World War I: November 1918-August 1931

    Europe After World War I: November 1918-August 1931

    World War I, also known as the Great War, left Germany and other countries humiliated and angry. Germany viewed the armistice that ended World War I as a truce, rather than a surrender. This view was ignored. Learn about events that led to World War II. See more »

  • Gallipoli Campaign

    Gallipoli Campaign

    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. See more »

  • Dirigible


    Dirigibleor Airship, a balloon that is self-propelled and that can be steered. There are three types: (1) the rigid dirigible, which holds its shape by means of a rigid metal framework around the gas cells; (2) the semirigid dirigible, which has a rigid keel along the bottom inside a single fabric gas bag, known as the envelope, but no framework around the envelope; and (3) the nonrigid dirigible, which holds its shape only by the pressure of the gas inside the fabric envelope. See more »

  • League of Nations

    League of Nations

    League of Nations, the association of countries formed at the end of World War I to prevent war and to promote international peace and security. See more »

  • Neutrality


    Neutrality, in international law, the state of noninterference and of peaceful relations that one nation maintains with two or more nations at war with each other. See more »

  • Selective Service System

    Selective Service System

    Selective Service System , an independent agency of the United States government. See more »

  • Tomb of the Unknowns

    Tomb of the Unknowns

    Unknowns, Tomb of the, a national memorial to the unrecovered dead of the United States armed forces of World Wars I and II and the Korean War. See more »

  • Treaties of Rapallo

    Treaties of Rapallo

    Rapallo, Treaties of, international agreements signed at Rapallo, Italy, soon after World War I. See more »

  • Treaty of Versailles

    Treaty of Versailles

    Versailles, Treaty of, the peace treaty at the end of World War I, signed on June 28, 1919, by Germany and by the Allied and Associated Powers. See more »

  • Triple Alliance

    Triple Alliance

    Triple Alliance, a name given to several international agreements. The most important was a secret treaty that was signed by Germany, Austria-Hungary, and Italy in 1882 and remained in effect until 1915. See more »

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