On July 28, 1914 the Austro-Hungarian Empire declared war on Serbia, citing Serbian involvement in the assassination of Archduke Franz Ferdinand the previous month. Ethnic nationalism, dynastic rivalry, and divisive alliances triggered a wave of hostilities, leaving almost the whole of Europe in a state of war within a few short weeks.
In the United States, many observers saw the Great War as an old world family quarrel. In 1916, Woodrow Wilson won a second term in the White House under the slogan, “He kept us out of the War.” This boast proved short-lived. The United State’s April 1917 entry into the war – the result of indiscriminate German submarine attacks in the Atlantic – was decisive, but wide swathes of public opinion questioned what had been billed as a “Crusade for Democracy.” In 1919, Congress vetoed the Treaty of Versailles over its inclusion of the League of Nations Charter (the forerunner of the United Nations). Wary of future foreign entanglements, America’s gaze shifted inwards, but the rise of totalitarianism in Europe and Asia brought isolationism to an end.
The last US veteran of World War One, Frank Woodruff Buckles, died in 2011. An NBC news profile, made shortly before his death, is below: