September 20 in Military History

The Greek fleet under Themistocles decisively defeated the Persian fleet of Xerxes I in the narrow straits off the island of Salamis near Athens. The victory, achieved by luring the larger Persian fleet into confined waters where their numbers became a disadvantage, saved Greek civilization and is considered one of the most important naval battles in history.

Portuguese navigator Ferdinand Magellan set sail from Sanlúcar de Barrameda, Spain, with five ships and 270 men on the expedition that would become the first circumnavigation of the globe. Though Magellan was killed in the Philippines in 1521, his voyage proved the Earth's true size and had profound military implications for colonial naval strategy.

Ferdinand Magellan's five-ship expedition sailed from Sanlucar de Barrameda, Spain, on a voyage that would complete the first circumnavigation of the globe. The expedition produced navigational and cartographic advances that reshaped naval operations for the next three centuries, including the first European transits of the strait that bears Magellan's name.

General Thomas held Snodgrass Hill against repeated Confederate assaults after the Union right collapsed, saving the Army of the Cumberland from destruction.

Italian troops breached the Aurelian Walls near the Porta Pia and captured Rome from the Papal States, completing the unification of Italy. Pope Pius IX retreated to the Vatican and declared himself a "prisoner," beginning the "Roman Question" that was not resolved until the Lateran Treaty of 1929.

The failure of the Jay Cooke and Company banking house triggered the Panic of 1873, a financial collapse that forced drastic cuts to the U.S. Army and Navy through the 1870s. The contraction left frontier outposts undermanned, stalled naval modernization, and shaped the thin red line of regular forces that fought the Plains Indian Wars.

Submarine I-25 of the Imperial Japanese Navy launched a Yokosuka E14Y floatplane that dropped incendiary bombs in the forest near Brookings, Oregon. It was the only aerial bombing attack of the continental United States during World War II and triggered expansion of West Coast air defense radar and civilian observer networks.

After eleven days of fierce fighting, the Allied beachhead at Salerno was finally secured as German forces began withdrawing toward the Volturno Line. The crisis that had nearly driven the invasion force back into the sea had passed, but the hard-won victory had cost the Allies over 12,000 casualties.

A Syrian armored division crossed into northern Jordan in support of Palestinian fedayeen battling King Hussein's army during the Black September crisis. Jordanian F-104 Starfighters and Centurion tanks destroyed dozens of Syrian T-54s and T-55s, checked the invasion, and shaped subsequent Middle East interstate confrontations.

President George W. Bush addressed a joint session of Congress nine days after the September 11 attacks. He identified al-Qaeda and the Taliban as responsible, demanded the Taliban surrender bin Laden, and warned that "every nation, in every region, now has a decision to make: either you are with us, or you are with the terrorists." The speech set the framework for the War on Terror.