September 6

Roman Emperor Theodosius I defeats and kills the usurper Eugenius at the Battle of the Frigidus.

Roman Emperor Theodosius I led his forces to a decisive victory over the usurper Eugenius, who had seized power in the western half of the empire with the backing of pagan Roman senators seeking to restore traditional religious practices. The victory secured Theodosius's position as sole ruler and reinforced Christianity's status as the empire's dominant faith.

Christopher Columbus departs the Canary Islands, beginning the Atlantic crossing of his first voyage.

Having assembled his three ships and crew at the Canary Islands for final provisioning and repairs, Columbus departed westward into open ocean, beginning the roughly five-week Atlantic crossing that would culminate in his historic landfall in the Caribbean. This departure point became a customary stopover for subsequent Spanish transatlantic voyages for generations afterward.

The Victoria arrives back in Spain, completing the first known circumnavigation of the globe.

Commanded during its final leg by Basque navigator Juan Sebastian Elcano after Ferdinand Magellan's death in the Philippines, the Victoria limped back into the Spanish port of Sanlucar de Barrameda with just 18 surviving crew members out of the original expedition's roughly 270. The ship's arrival confirmed the completion of history's first circumnavigation of the globe.

The Mayflower departs Plymouth, England, carrying Pilgrims bound for North America.

Carrying 102 passengers, many of them religious separatists seeking freedom to practice their faith away from the Church of England, the Mayflower set sail after an earlier failed attempt alongside a companion ship that proved unseaworthy. The roughly two-month Atlantic crossing brought the Pilgrims to present-day Massachusetts, where they established the Plymouth Colony.

Chemist John Dalton begins using symbols to represent atoms of different elements, an early step toward modern atomic theory.

Building on the ancient Greek concept of indivisible atoms, Dalton proposed that each chemical element consisted of uniquely weighted atoms and developed a system of circular symbols to represent them in chemical diagrams, an early visual language for expressing chemical composition. His broader atomic theory, developed around the same period, laid crucial groundwork for the modern science of chemistry.

President William McKinley is shot by anarchist Leon Czolgosz at the Pan-American Exposition in Buffalo, New York.

While greeting the public at the Pan-American Exposition in Buffalo, President McKinley was shot twice at close range by self-proclaimed anarchist Leon Czolgosz. McKinley initially appeared to be recovering but died eight days later from infection related to his wounds, elevating Vice President Theodore Roosevelt to the presidency and prompting increased Secret Service protection for future presidents.

The First Battle of the Marne halts the German army's advance into France, a turning point in the war's opening weeks.

After German forces had advanced to within striking distance of Paris, a determined Allied counterattack along the Marne River forced the German army into a strategic retreat, ending hopes of a swift victory envisioned under the German war plan. The battle's outcome effectively locked both sides into the prolonged trench warfare that would define most of the remaining conflict.

Palestinian militants take Israeli athletes hostage at the Munich Olympics, resulting in the deaths of nine athletes in what becomes known as the Munich massacre.

During the Munich Summer Olympics, members of the Palestinian militant group Black September infiltrated the Olympic Village, killing two Israeli team members immediately and taking nine others hostage. A botched rescue attempt at a nearby airport resulted in the deaths of all nine remaining hostages, along with a German police officer and five of the eight attackers.

The Soviet Union formally recognizes the independence of the three Baltic states.

As the Soviet Union's central authority rapidly disintegrated following the failed August coup against Mikhail Gorbachev, the State Council of the USSR formally acknowledged the restored independence of Estonia, Latvia, and Lithuania, nations that had been forcibly annexed by the Soviet Union in 1940. Their independence was quickly recognized internationally as well.

Liz Truss becomes Prime Minister of the United Kingdom, succeeding Boris Johnson.

Following Boris Johnson's resignation amid mounting political scandals, Liz Truss traveled to Balmoral Castle to be formally appointed prime minister by Queen Elizabeth II, in what would prove to be one of the monarch's final official acts before her death just two days later. Truss's own tenure in office lasted only 49 days, the shortest of any British prime minister in history.