Robert Lansing was an American lawyer and diplomat who served as Counselor to the State Department at the outbreak of World War I, and then as United States Secretary of State under President Woodrow Wilson from 1915 to 1920. A conservative pro-business Democrat, he was a strong advocate of democracy and of the United States' role in establishing international law. He was an avowed enemy of German autocracy and Russian Bolshevism. Before U.S. involvement in the war, Lansing vigorously advocated freedom of the seas and the rights of neutral nations. He later advocated U.S. participation in World War I, negotiated the Lansing–Ishii Agreement with Japan in 1917 and was a member of the American Commission to Negotiate Peace at Paris in 1919. However, Wilson made Colonel House his chief foreign policy advisor because Lansing privately opposed much of the Treaty of Versailles and was skeptical of the Wilsonian principle of self-determination.

The Treaty of Versailles was a peace treaty signed on 28 June 1919. As the most important treaty of World War I, it ended the state of war between Germany and most of the Allied Powers. It was signed in the Palace of Versailles, exactly five years after the assassination of Archduke Franz Ferdinand, which led to the war. The other Central Powers on the German side signed separate treaties. Although the armistice of 11 November 1918 ended the actual fighting, and agreed certain principles and conditions including the payment of reparations, it took six months of Allied negotiations at the Paris Peace Conference to conclude the peace treaty. Germany was not allowed to participate in the negotiations before signing the treaty.