1921

1921 was a year of postwar realignment and political experimentation. In the Soviet Union, the government introduced the New Economic Policy to revive the economy after the civil war, while the Kronstadt rebellion and its suppression underscored the regime's authority. The year also saw major territorial shifts and the emergence of movements that would shape the decade.

Poland and Soviet Russia concluded the Polish-Soviet War with the Riga Peace Treaty in March 1921, defining borders that persisted for years. In December, Ireland signed the Anglo-Irish Treaty, establishing the Irish Free State and leaving Northern Ireland under British rule. The Chinese Communist Party was founded in Shanghai in July 1921, marking the birth of a major political movement. The Washington Naval Conference began in November 1921 to discuss naval disarmament, and the United States enacted the Emergency Quota Act restricting immigration.

The Tulsa Race Massacre occurred in late May and early June 1921 in Oklahoma, resulting in the deaths and destruction of a prosperous Black neighborhood. In the Soviet Union, the ongoing famine of 1921–22 followed wartime requisitioning and contributed to social and political pressures during the year.

On the scientific front, Frederick Banting and Charles Best discovered insulin in 1921, a breakthrough that transformed diabetes treatment and later earned a Nobel Prize.