World War I decimated millions and profoundly altered the course of world history. Postwar instabilities led directly toward a global depression and a second world war. The war sparked the Bolshevik revolution that the United States later engaged in Cold War. It created Middle Eastern nations and aggravated ethnic tensions that the United States could never tackle. By fighting with and against European powers on the Western Front, America’s place in the world was never the same. By whipping up nationalist passions, American attitudes toward radicalism, dissent, and immigration were poisoned. Postwar disillusionment shattered Americans’ hopes for the progress of the modern world. The war came and went, and left in its place the bloody wreckage of an old world through which the world travelled to a new and uncertain future.

This chapter was edited by Paula Fortier, with content contributions by Tizoc Chavez, Zachary W. Dresser, Blake Earle, Morgan Deane, Paula Fortier, Larry A. Grant, Mariah Hepworth, Jun Suk Hyun, and Leah Richier.