Read this overview of the period of the U.S. involvement in World War I. The account includes preludes to war and postwar instabilities and their effects.
Conclusion
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, which led to the Soviet Union and later the Cold War. It
created Middle Eastern nations and aggravated ethnic tensions that the
United States could never overcome. And the United States had fought on
the European mainland as a major power. 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, leaving in its place the bloody
wreckage of an old world through which the United States traveled to a
new and uncertain future.