December 20 in Military History

The United States formally took possession of the Louisiana Territory from France at a ceremony in New Orleans, doubling the size of the nation for $15 million. The acquisition eliminated a major foreign military presence on America's western border and gave the United States control of the Mississippi River, the strategic waterway that would be the central theater of the Civil War six decades later.

South Carolina became the first state to secede from the Union, voting unanimously at a convention in Charleston. The secession, driven by the election of Abraham Lincoln and fears that his administration would restrict slavery, triggered a cascade of six more states leaving the Union by February 1861 and set the stage for the deadliest war in American history.

A convention of delegates meeting in Charleston voted unanimously, 169 to 0, to dissolve South Carolina's union with the other states. The secession ordinance triggered the chain of state conventions that would produce the Confederate States of America within six weeks and the firing on Fort Sumter within four months, beginning the most destructive military conflict ever fought on American soil.

The final elements of the Australian and New Zealand Army Corps evacuated the beaches at Anzac Cove and Suvla Bay on the Gallipoli Peninsula without a single casualty, one of the most successful deception and withdrawal operations in military history. The evacuation ended the allied effort to force the Dardanelles and opened the Ottoman Empire's full weight against Russia on the Caucasus front.

The American Volunteer Group, the legendary "Flying Tigers" under Colonel Claire Chennault, flew their first combat mission, intercepting Japanese bombers over Kunming, China. Flying P-40 Warhawks with their iconic shark-mouth nose art, the volunteers shot down several Japanese aircraft while suffering no losses, beginning one of the most celebrated aerial campaigns of World War II.

The American Volunteer Group, better known as the Flying Tigers, flew its first combat mission, intercepting ten Japanese Ki-21 bombers headed for Kunming, China. Using P-40B Tomahawk fighters flown by former U.S. Army, Navy, and Marine pilots commanded by Colonel Claire Lee Chennault, the group destroyed four Japanese bombers with no American losses in combat.

Canadian troops of the 1st Canadian Infantry Division entered the town of Ortona on the Adriatic coast of Italy and began eight days of close-quarters urban combat against German 1st Parachute Division troops. The fighting, later called "Little Stalingrad" by German accounts, forced Canadian engineers and infantry to develop new urban combat tactics including "mouse-holing" through building walls to avoid street-level fire.

German forces completed the encirclement of Bastogne, Belgium, trapping the 101st Airborne Division and elements of other units in a pocket with no supplies except what could be airdropped. Despite being outnumbered, outgunned, and freezing in their foxholes, the "Battered Bastards of Bastogne" refused to give up, their defiance would become the defining story of the Battle of the Bulge.

In the early morning hours, 24,000 American troops launched Operation Just Cause, the invasion of Panama to depose dictator Manuel Noriega, who had been indicted on drug trafficking charges and had annulled democratic elections. The assault, the largest U.S. combat operation since the Vietnam War, used coordinated strikes by paratroopers, Rangers, Marines, and Special Operations forces against 27 targets simultaneously across Panama City and the Canal Zone.

United States ground, air, and naval forces launched Operation Just Cause across Panama at 1 a.m. local time, attacking 27 targets simultaneously in the largest American combat operation since the Vietnam War. The operation sought to remove Panamanian leader Manuel Noriega, protect American citizens, restore democracy, and secure the Panama Canal. Noriega evaded capture at the Comandancia and took refuge in the Papal Nunciature on Christmas Eve.