September 21

Events

455day.year

Emperor Avitus enters Italy with a Gallic army and consolidates his power.

In 455 AD, Emperor Avitus crossed the Alps with a Gallic force to enter Italy and assert his authority over the Western Roman Empire.
By 455, the Western Roman Empire was weakened by internal strife and external pressures. Avitus, previously a Roman general with strong ties to the Gallic aristocracy, secured support from local Gallic tribes. On September 21, he led a Gallic army across the Alps into Italy, aiming to fill the power vacuum left by deposed emperors. His march marked a rare alliance between Roman and Gallic elements, reflecting shifting power dynamics in late antiquity. Upon entering Italy, Avitus consolidated his position by securing key cities and gaining recognition from Roman elites. Though his rule would be short-lived, his accession highlighted the fragmentation and regionalization of imperial authority. The event underscored the complexity of identities and loyalties as the Western Empire neared its decline.
455 Avitus Italy
1170day.year

Anglo-Norman invasion of Ireland: The Kingdom of Dublin falls to Anglo-Norman invaders.

On September 21, 1170, Anglo-Norman forces captured the Kingdom of Dublin, marking a crucial step in the Norman conquest of Ireland.
In the summer of 1170, Anglo-Norman knights under Richard de Clare sought to extend their influence across Ireland. After landing in Ireland earlier that month, they advanced on Dublin, the richest and most fortified Norse-Gaelic city. On September 21, a combined force of Norman knights and Irish allies breached the city defenses. The fall of Dublin provided the Normans with a strategic coastal stronghold and a base for further operations. The capture altered power relations on the island, signaling the beginning of centuries of Norman and later English involvement in Ireland. Local Irish kings would struggle to resist the Normans, leading to profound political and cultural changes. The event laid foundations for the complex Anglo-Irish history that would shape the region for generations.
1170 Anglo-Norman invasion of Ireland Kingdom of Dublin Anglo-Norman
1217day.year

Livonian Crusade: The Estonian leader Lembitu and Livonian leader Caupo of Turaida are killed in the Battle of St. Matthew's Day.

During the Livonian Crusade, the allied pagan leaders Lembitu and Caupo of Turaida died in the Battle of St. Matthew's Day in 1217.
The Livonian Crusade sought to convert Baltic tribes to Christianity under the auspices of the Teutonic Knights. Estonian leader Lembitu, a unifying figure among the tribes, and Livonian chief Caupo of Turaida, an early Christian convert, met on the battlefield on September 21, 1217. Despite their divergent beliefs, the two leaders had formed a temporary alliance to resist German crusaders. The battle, fought on St. Matthew's Day, ended in a decisive defeat, and both leaders were killed in combat. Their deaths marked a turning point, weakening native resistance and accelerating the Christianization and political subjugation of the Baltic peoples. The aftermath saw the expansion of Germanic rule and the establishment of ecclesiastical states that would endure for centuries. The event highlights the complex interplay of faith, power, and identity in medieval Northern Europe.
1217 Livonian Crusade Lembitu Caupo of Turaida Battle of St. Matthew's Day
1435day.year

The Treaty of Arras is promulgated, causing Burgundy to switch sides in the Hundred Years' War.

The Treaty of Arras of 1435 realigned alliances in the Hundred Years' War, as Burgundy abandoned England and reconciled with France.
Signed on September 21, 1435, the Treaty of Arras ended decades of rivalry between Charles VII of France and Philip the Good, Duke of Burgundy. Under its terms, Burgundy recognized the French king's legitimacy in exchange for territorial and financial concessions. This diplomatic breakthrough deprived England of its powerful Burgundian ally, shifting the balance in the Hundred Years' War. The treaty followed the earlier Treaty of Troyes, which had disinherited the Dauphin in favor of an English heir. Philip the Good's decision reflected his desire to secure his duchy's borders and trade interests, particularly with the economically vital Burgundian Netherlands. The realignment accelerated French military successes, contributing to the eventual expulsion of the English from most of France. The Treaty of Arras remains a landmark in medieval diplomacy, illustrating the fluidity of loyalties in feudal politics.
1435 Treaty of Arras Burgundy Hundred Years' War
1745day.year

A British government army led by Sir John Cope is defeated in less than 15 minutes by the Jacobite forces of Prince Charles Edward Stuart.

On September 21, 1745, the Jacobite army under Prince Charles Edward Stuart overwhelmed Sir John Cope's forces at the Battle of Prestonpans in under fifteen minutes.
The skirmish at Prestonpans marked the opening clash of the Jacobite rising of 1745. Sir John Cope, commanding roughly 1,500 government troops, faced a similar number of Highland Jacobites racing south toward Edinburgh. On the morning of September 21, the Jacobites executed a surprise bayonet charge across marshy ground, catching Cope's men off guard. In less than fifteen minutes, the government line collapsed, yielding a decisive Jacobite victory. The rout boosted Highland morale and enabled Charles Edward Stuart, known as the Young Pretender, to occupy Edinburgh shortly thereafter. Though the uprising ultimately ended in defeat at Culloden in 1746, Prestonpans demonstrated the formidable spirit of the Jacobite clans. The event has since been immortalized in Scottish ballads and military histories for its dramatic brevity and impact.
1745 Sir John Cope defeated Jacobite Prince Charles Edward Stuart
1776day.year

Part of New York City is burned shortly after being occupied by British forces.

After British forces occupied New York City in September 1776, a fire swept through Lower Manhattan, causing widespread destruction.
In the wake of the Battle of Long Island, British troops under General Howe entered New York City in mid-September 1776. On September 21, a massive fire broke out in the occupied city, destroying homes, warehouses, and public buildings in Lower Manhattan. Controversy surrounds the blaze, with both British and American accounts accusing the other side of arson. The inferno consumed some 500 structures, leaving hundreds of civilians homeless and crippling local commerce. Despite the destruction, the British used New York as a key strategic base for the remainder of the Revolutionary War. The event underscored the human cost of war and fueled American resentment toward occupying forces. The remains of burned districts were later rebuilt, shaping the city's future urban landscape.
1776 New York City burned
1780day.year

American Revolutionary War: Benedict Arnold gives the British the plans to West Point.

On September 21, 1780, American General Benedict Arnold met with the British, providing them with detailed plans to capture West Point.
Benedict Arnold, once a celebrated hero of the American Revolution, grew disillusioned with Continental Congress and his own treatment. In early 1780, he began secret negotiations with British Major John Andre to betray the strategic fort at West Point. On September 21, Arnold guided Andre aboard the HMS Vulture in the Hudson River, handing over maps and defensive documents. His treason threatened to hand control of West Point to British forces, which would have split the colonies in two. By late September, Andre was captured with incriminating papers, and Arnold's plot was uncovered. Arnold escaped to New York City, where he received a commission in the British Army, leaving his American reputation in ruins. The incident remains one of the most infamous acts of betrayal in U.S. history, highlighting the fragile loyalties of war.
1780 American Revolutionary War Benedict Arnold
1792day.year

French Revolution: The National Convention abolishes the monarchy.

On September 21, 1792, the French National Convention officially abolished the monarchy, declaring the First French Republic.
Amidst the radical phase of the French Revolution, the newly elected National Convention convened in Paris in September 1792. Facing internal unrest and foreign invasion, delegates voted on September 21 to end centuries of hereditary rule. The abolition of the monarchy led to the imprisonment of King Louis XVI and the proclamation of the Republic the following day. This momentous decision cut ties with traditional symbols of power and paved the way for revolutionary reforms. Republican leaders like Robespierre and Danton soon emerged as central figures in the new government. The move intensified the Revolutionary Wars and ushered in the Reign of Terror. The establishment of the First French Republic on September 22 cemented France's radical political transformation.
1792 French Revolution National Convention abolishes the monarchy
1809day.year

British Secretary of War Lord Castlereagh and Foreign Secretary George Canning meet in a duel on Putney Heath, with Castlereagh wounding Canning in the thigh.

On September 21, 1809, British statesmen Lord Castlereagh and George Canning fought a duel on Putney Heath after a heated Cabinet dispute.
In early 1809, heated political tensions arose within the Ministry regarding Britain's war strategy against Napoleon. Lord Castlereagh, serving as Secretary of War, accused Foreign Secretary George Canning of undermining government unity. Unable to resolve their differences, the two men agreed to a formal duel on September 21 at Putney Heath. Each fired a single shot; Castlereagh's bullet grazed Canning's thigh, ending the affair without fatalities. Though illegal, the duel was tacitly condoned by their peers as a means of defending personal honor. The incident shocked the public and underscored the passionate nature of early 19th-century politics. Both men later entered Parliament as Prime Minister, with their friendship and rivalry shaping Britain's post-war era.
1809 Secretary of War Lord Castlereagh Foreign Secretary George Canning duel Putney Heath
1843day.year

The crew of schooner Ancud, led by John Williams Wilson, takes possession of the Strait of Magellan on behalf of the Chilean government.

On September 21, 1843, the schooner Ancud claimed sovereignty over the Strait of Magellan for Chile under the leadership of John Williams Wilson.
Chile sought to secure control of the strategic sea route at the southern tip of South America, coveted by global powers. Captain John Williams Wilson was tasked with leading the schooner Ancud to formally occupy the strait. On September 21, 1843, Wilson and his crew landed on Tierra del Fuego and raised the Chilean flag. The act established Chilean jurisdiction over the waterway, ensuring safe passage for national and international vessels. This expedition bolstered Chile's claim to Patagonia and strengthened its maritime presence. The occupation preempted potential claims by European nations and laid groundwork for future settlement and trade. Today, the Strait of Magellan remains a vital channel linking the Atlantic and Pacific Oceans, a testament to Chile's early naval ambition.
1843 schooner Ancud John Williams Wilson takes possession Strait of Magellan
1860day.year

Second Opium War: An Anglo-French force defeats Chinese troops at the Battle of Palikao.

At the Battle of Palikao, Anglo-French forces decisively defeat Qing troops, opening the way for further concessions in China.
Fought on September 21, 1860, the Battle of Palikao saw combined British and French armies clash with Qing dynasty forces. Under General Cousin-Montauban and Lord Elgin, the allies used superior artillery to breach Chinese defenses. The defeat opened the route to Beijing and pressured the imperial court into negotiations. This engagement marked a turning point in the Second Opium War, demonstrating Western military dominance. The subsequent treaties expanded foreign trade rights and diplomatic privileges in China.
1860 Second Opium War Battle of Palikao
1862day.year

Taiping Rebellion: The Ever Victorious Army defeats Taiping forces at the Battle of Cixi.

The Ever Victorious Army led by Western officers defeats Taiping rebels at Cixi, securing a key Qing victory.
On September 21, 1862, the Qing government’s Ever Victorious Army routed Taiping Rebel forces at Cixi. Commanded by foreign officers such as Frederick Townsend Ward and later Charles Gordon, this unit combined Western military tactics with local troops. The victory halted the southward advance of the Taiping Heavenly Kingdom and bolstered Qing morale. It showcased the growing influence of foreign military advisors in China’s internal conflicts. Although the rebellion continued until 1864, the setback at Cixi weakened the Taiping movement significantly.
1862 Taiping Rebellion Ever Victorious Army Battle of Cixi