1176day.year
The Battle of Myriokephalon is the last attempt by the Byzantine Empire to recover central Anatolia from the Seljuk Turks.
In 1176, the Byzantine Empire's final campaign to reclaim central Anatolia ends in defeat at the Battle of Myriokephalon against the Seljuk Turks.
The Battle of Myriokephalon on September 17, 1176, saw the forces of Emperor Manuel I Komnenos ambushed by the Seljuk Turks in the Tectorian Mountains. Despite fielding a well-trained army, the Byzantines suffered significant losses and failed to break Seljuk control over Anatolia. The defeat dashed Byzantine hopes of restoring their eastern territories and marked a turning point in the empire's decline. It highlighted the effectiveness of Turkish tactics and fortified Anatolian defenses. The battle's outcome shaped subsequent diplomatic relations and undermined Byzantine influence in the region.
1176
Battle of Myriokephalon
1462day.year
Thirteen Years' War: A Polish army under Piotr Dunin decisively defeats the Teutonic Order at the Battle of Świecino.
During the Thirteen Years' War in 1462, Piotr Dunin leads Polish forces to a decisive victory over the Teutonic Knights at Świecino.
On September 17, 1462, Polish troops commanded by Piotr Dunin confronted the Teutonic Order near the village of Świecino. Employing effective tactics and superior numbers, the Poles routed the Teutonic cavalry, inflicting heavy casualties. This victory weakened the Order's position in Pomerania and bolstered Polish claims in the region. The outcome shifted momentum in favor of King Casimir IV and laid groundwork for the eventual peace settlement. The battle remains celebrated in Polish history as a symbol of national resilience and military prowess.
1462
Thirteen Years' War
Battle of Świecino
1620day.year
Polish–Ottoman War: The Ottoman Empire defeats the Polish–Lithuanian Commonwealth during the Battle of Cecora.
In 1620, Ottoman forces defeat the Polish–Lithuanian Commonwealth at the Battle of Cecora, marking a turning point in the Polish–Ottoman War.
On September 17, 1620, troops of the Ottoman Empire clashed with the forces of the Polish–Lithuanian Commonwealth near Cecora, in present-day Romania. The battle ended in a decisive Ottoman victory, aided by tactical surprise and superior cavalry. Polish hetman Stanisław Żółkiewski was killed during a rear-guard action, dealing a blow to Commonwealth morale. The defeat opened the way for further Ottoman incursions and underscored vulnerabilities in the Commonwealth's eastern defenses. The outcome prompted subsequent diplomatic negotiations and military reforms on both sides.
1620
Polish–Ottoman War
Battle of Cecora
1631day.year
Sweden wins a major victory at the Battle of Breitenfeld against the Holy Roman Empire during the Thirty Years' War.
At the Battle of Breitenfeld in 1631, Swedish King Gustavus Adolphus secures a pivotal victory over the Holy Roman Empire during the Thirty Years' War.
The Battle of Breitenfeld, fought on September 17, 1631, marked the first major Protestant success in the Thirty Years' War. King Gustavus Adolphus of Sweden employed innovative tactics and disciplined infantry to defeat the Catholic League forces led by Count Tilly. The triumph opened central Germany to Swedish influence and galvanized Protestant states to join his cause. Gustavus Adolphus's reforms in artillery and combined arms became a model for European armies. The victory shifted the war's momentum and elevated Sweden as a great military power.
1631
Battle of Breitenfeld
Thirty Years' War
1658day.year
The Battle of Vilanova is fought between Portugal and Spain during the Portuguese Restoration War.
In 1658, Portuguese troops engage Spanish forces at the Battle of Vilanova, pressing their fight for restored independence.
The Battle of Vilanova took place on September 17, 1658, as part of the ongoing Portuguese Restoration War (1640–1668). Portuguese troops engaged Spanish invaders near Vilanova de Cerveira in a fierce encounter. Although tactically indecisive, the engagement demonstrated Portugal's resilience and bolstered national morale. Commanders on both sides tested new field tactics reflective of mid-17th-century warfare. The battle contributed to the protracted stalemate that ultimately led to Spain's recognition of Portuguese sovereignty in 1668.
1658
Battle of Vilanova
Portuguese Restoration War
1775day.year
American Revolutionary War: The invasion of Quebec by the Continental Army begins with the Siege of Fort St. Jean.
The Continental Army begins its siege of Fort St. Jean, launching an ambitious invasion of Quebec during the American Revolutionary War.
In September 1775, General Richard Montgomery led Continental forces northward from New York to strike at British-held Canada.
They laid siege to Fort St. Jean, the key defensive position guarding the Richelieu River corridor.
The campaign aimed to bring the French-speaking province of Quebec into the rebellion against British rule.
Troops faced harsh wilderness terrain, severe supply shortages, and the challenge of coordinating American and Canadian irregulars.
Despite early successes, the siege stalled as seasonal weather worsened and the garrison held firm.
Although the attempt to seize Quebec City ultimately failed, the offensive demonstrated the Colonies’ resolve and broadened the scope of the Revolutionary War.
1775
American Revolutionary War
invasion of Quebec
Continental Army
Siege of Fort St. Jean
1793day.year
War of the Pyrenees: France defeats a Spanish force at the Battle of Peyrestortes.
French Republican forces defeat Spain at the Battle of Peyrestortes, securing control of the Roussillon region during the War of the Pyrenees.
On September 17, 1793, during the War of the Pyrenees, French Republican forces engaged Spanish troops at Peyrestortes near Perpignan.
Effective artillery support and infantry maneuvers broke the Spanish defensive line in Roussillon.
Spanish soldiers were pushed back toward Figueres, relieving the besieged French positions.
The victory bolstered the revolutionary government in Paris, which faced multiple external threats.
It showcased the resilience of citizen-soldiers and the growing prowess of France’s new armies.
This success helped secure France’s southern frontier and disrupted Spain’s military campaign.
1793
War of the Pyrenees
Battle of Peyrestortes
1794day.year
Flanders Campaign: France completes its conquest of the Austrian Netherlands at the Battle of Sprimont.
French armies complete their conquest of the Austrian Netherlands with a decisive victory at the Battle of Sprimont.
In the Flanders Campaign of the French Revolutionary Wars, French forces clashed with Austria near Sprimont on September 17, 1794.
Crossing flooded fields and defensive earthworks, the French broke Austrian lines in a daring assault.
Exhausted and outnumbered, the Austrian army withdrew toward Liège, conceding control of the Austrian Netherlands.
This victory completed France’s conquest of the region and led to its annexation into the revolutionary state.
It underscored the effectiveness of mass conscript armies employing aggressive tactics.
The battle also highlighted revolutionary France’s ability to project power deep into the Low Countries.
1794
Flanders Campaign
Battle of Sprimont
1809day.year
Peace between Sweden and Russia in the Finnish War; the territory that will become Finland is ceded to Russia by the Treaty of Fredrikshamn.
Sweden and Russia sign the Treaty of Fredrikshamn, ending the Finnish War and ceding Finland to the Russian Empire.
On September 17, 1809, Sweden and Russia concluded the Finnish War with the signing of the Treaty of Fredrikshamn.
By its terms, Sweden ceded Finland and the Åland Islands to Russia, ending over six centuries of Swedish rule.
Finland became an autonomous Grand Duchy under the Russian Empire, retaining local laws and institutions.
The new status fostered a distinct Finnish identity and laid groundwork for future nationhood.
Sweden emerged diminished, while Russia secured a strategic buffer against Western powers.
The treaty exemplified the era’s shifting alliances and territorial realignments during the Napoleonic Wars.
1809
Finnish War
Treaty of Fredrikshamn
1861day.year
Argentine Civil Wars: The State of Buenos Aires defeats the Argentine Confederation at the Battle of Pavón.
The State of Buenos Aires wins the Battle of Pavón against the Argentine Confederation, influencing Argentina's national unification.
On September 17, 1861, the Battle of Pavón saw Buenos Aires forces under Bartolomé Mitre confront the Argentine Confederation’s army led by Justo José de Urquiza.
Despite being outnumbered, Mitre’s troops leveraged superior tactics and artillery to pressure Urquiza’s lines.
Confederation forces withdrew from the field, effectively ceding victory to the State of Buenos Aires.
This outcome paved the way for the reunification of Argentina under Mitre’s presidency and centralized national governance.
Mitre later became the first president of a unified Argentina, centralizing political authority in the capital.
Pavón’s legacy influenced Argentina’s transition from provincial conflicts to a cohesive nation-state.
1861
Argentine Civil Wars
Battle of Pavón
1862day.year
American Civil War: George B. McClellan's Army of the Potomac halts the first invasion of the North by Robert E. Lee and his Army of Northern Virginia in the single-day Battle of Antietam, the bloodiest day in American military history.
At the Battle of Antietam, McClellan's Army of the Potomac halted Lee's first invasion of the North in the bloodiest single day in American military history.
On September 17, 1862, the clash at Antietam Creek in Maryland marked the climax of Confederate General Robert E. Lee's first invasion of Northern soil. Union General George B. McClellan's Army of the Potomac confronted Lee's Army of Northern Virginia in a fiercely contested day-long battle. Intense fighting erupted around key positions such as the Cornfield, Dunker Church, and the Sunken Road. By nightfall, both sides suffered over 22,000 casualties, making it the deadliest single day in American military history. The Union's tactical stand forced Lee to retreat back to Virginia, providing a strategic advantage to the North. President Abraham Lincoln leveraged the Union's performance to issue the preliminary Emancipation Proclamation shortly thereafter, shifting the war's moral and political stakes. The engagement at Antietam remains a turning point that shaped the course of the Civil War.
1862
American Civil War
George B. McClellan
Army of the Potomac
invasion
North
Robert E. Lee
Army of Northern Virginia
Battle of Antietam
1862day.year
American Civil War: The Allegheny Arsenal explosion in Lawrenceville, Pennsylvania results in the single largest civilian disaster during the war.
The 1862 Allegheny Arsenal explosion in Pennsylvania became the Civil War's single largest civilian disaster.
On September 17, 1862, a massive explosion ripped through the Allegheny Arsenal in the Lawrenceville neighborhood of Pittsburgh. The arsenal, a key supplier of ammunition for the Union Army, experienced a tragic malfunction in its powder magazine. Over 700 workers were on site, and the blast claimed the lives of 78 people, most of them young women and girls. The cause of the explosion remains a subject of historical debate, with theories ranging from accidental ignition to sabotage. As the deadliest civilian accident of the Civil War, the disaster highlighted the wartime demand's toll on homefront munitions factories. The explosion prompted reviews of safety protocols at similar facilities nationwide. The memory of the tragedy endures in local memorials and Pennsylvania's industrial history.
Allegheny Arsenal
Lawrenceville, Pennsylvania