July 21 in Military History

English lookouts spot the Spanish Armada approaching the English Channel, beginning the running naval battle that would end Spain's invasion attempt and establish England as a rising naval power.

Napoleon Bonaparte defeats the Mamluk army in sight of the Great Pyramids of Giza, securing French control of Egypt and establishing Napoleon's reputation as one of history's great military commanders.

Union and Confederate armies clash for the first time in a major engagement at Manassas Junction, Virginia. The Union rout shatters Northern illusions of a quick war and transforms "Stonewall" Jackson into a Confederate legend.

The Great Railroad Strike of 1877 reaches its most violent phase in Pittsburgh, where Pennsylvania militia fire on strikers and crowds burn 104 locomotives and over 2,000 freight cars, leading to federal troop deployments that redefined Army's role in domestic disturbances.

Senior Austro-Hungarian civilian and military leaders in Vienna complete the text of the July 23 ultimatum to Serbia, a deliberately unacceptable diplomatic document drafted to trigger the war that would become World War I.

The Scopes Trial in Dayton, Tennessee ends with a guilty verdict against teacher John T. Scopes, a civilian case whose legal arguments by Clarence Darrow and William Jennings Bryan shaped later debates over science education in American military academies.

U.S. Marines of the 3rd Marine Division and 1st Provisional Marine Brigade storm the beaches of Guam, beginning the campaign to recapture the first American territory lost in World War II from the Japanese.

The Nazi regime begins executing participants in the July 20 plot against Hitler. Over the following months, more than 200 conspirators are killed, many by slow strangulation with piano wire, their deaths filmed for Hitler's viewing.

The nuclear-powered cargo ship NS Savannah is launched at Camden, New Jersey, demonstrating civilian applications of naval reactor technology under President Eisenhower's Atoms for Peace initiative and previewing the reactor designs used aboard U.S. Navy surface ships.

Sirimavo Bandaranaike is sworn in as Prime Minister of Ceylon, the first woman in history to lead a national government, and inherits a military establishment rebuilt from colonial Ceylon Defence Forces into an independent national army.

Neil Armstrong and Buzz Aldrin conduct humanity's first extravehicular activity on the lunar surface, planting the American flag and collecting lunar samples before returning to the Eagle lunar module.