May 20 in Military History

English royalist forces under William Marshal, at age 70 the greatest knight in Christendom, routed a French invasion army at Lincoln. The victory turned the tide of the First Barons' War and preserved the throne for the young Henry III, securing the future of the Magna Carta.

North Carolina became the last of the eleven Confederate states to secede, completing the formation of the Confederacy. The state would provide more troops to the Confederate army than any other and suffer more casualties, including the devastating losses at Gettysburg's Pickett's Charge.

Confederate forces attacked Butler's Army of the James at Ware Bottom Church, Virginia, forcing the Union troops back and effectively bottling them up on the Bermuda Hundred peninsula between the James and Appomattox Rivers. Grant would later describe Butler as "corked in a bottle."

The Republic of Cuba formally declared its independence and Tomas Estrada Palma was inaugurated as the first Cuban president, ending three and a half years of U.S. military occupation after the Spanish-American War. The U.S. retained the right under the Platt Amendment to intervene militarily and kept the Guantanamo Bay naval station.

Ottoman and Allied commanders at Gallipoli agreed to a nine-hour armistice for the burial of the dead from the previous weeks of fighting around ANZAC Cove. The truce produced one of the most remarkable moments of cross-line humanity in the Great War and influenced the evolution of the laws of armed conflict.

U.S. Army Air Service reserve pilot Charles Lindbergh took off from Roosevelt Field on Long Island in the Ryan NYP monoplane Spirit of St. Louis, beginning the first solo non-stop transatlantic flight. The 33.5-hour crossing to Paris transformed aviation and accelerated American and European investment in long-range military aircraft.

Amelia Earhart took off from Harbour Grace, Newfoundland, in a single-engine Lockheed Vega 5B on the flight that would make her the first woman to fly solo across the Atlantic. The 14-hour, 56-minute crossing ended in a cow pasture in Northern Ireland and reshaped public expectations for long-range aircraft and crew endurance.

Germany launched the largest airborne invasion in history on Crete. Though successful, the devastating losses convinced Hitler to never authorize another major airborne assault.

The United States dropped the first airborne hydrogen bomb from a B-52 bomber over Bikini Atoll during Operation Redwing. The test, codenamed Cherokee, demonstrated the ability to deliver thermonuclear weapons by air, making the bomber fleet a credible nuclear deterrent and accelerating the arms race.

Premier Li Peng declared martial law in Beijing, authorizing the People's Liberation Army to deploy into the capital and restore order during the Tiananmen Square protests. The resulting military operation on June 4 killed hundreds of civilians and reshaped China's internal security apparatus for a generation.

The last Ukrainian defenders at the Azovstal steel plant in Mariupol surrendered after a nearly three-month siege. The defenders' resistance had tied down significant Russian forces and provided crucial time for Ukraine to organize its defenses elsewhere, becoming a symbol of Ukrainian determination.