American history

First World War (1917–1918)

Previously isolationist, the United States became involved in Europe during the First World War, a world conflict occurring from 1914 to 1918. No previous conflict had mobilized so many soldiers or involved so many in the field of battle. Never before had casualties been so high.

Chemical weapons were used for the first time, the first mass bombardment of civilians from the sky was executed, and some of the century's first large-scale civilian massacres took place.

Four dynasties, the Habsburgs, the Romanovs, the Ottomans and the Hohenzollerns, who had roots of power back to the days of the Crusades, all fell after the war.