September 12 is the 255th day of the year in the Gregorian calendar. There are 110 days remaining until the end of the year.
490 BC – Battle of Marathon: The conventionally accepted date for the Battle of Marathon. The Athenians and their Plataean allies, defeat the first Persian invasion force of Greece.
372 – Sixteen Kingdoms: Jin Xiaowudi, age 10, succeeds his father Jin Jianwendi as Emperor of the Eastern Jin dynasty.
1185 – Emperor Andronikos I Komnenos brutally put to death in Constantinople.
1213 – Albigensian Crusade: Simon de Montfort, 5th Earl of Leicester, defeats Peter II of Aragon at the Battle of Muret.
1229 – Battle of Portopí: The Aragonese army under the command of James I of Aragon disembarks at Santa Ponça, Majorca, with the purpose of conquering the island.
1309 – The First Siege of Gibraltar takes place in the context of the Spanish Reconquista pitting the forces of the Kingdom of Castile against the Emirate of Granada resulting in a Castilian victory.
1609 – Henry Hudson begins his exploration of the Hudson River while aboard the Halve Maen.
1656 – A gunpowder factory explodes in Valletta, Malta, killing 22 people and damaging several buildings.
1683 – Austro-Ottoman War: Battle of Vienna: Several European armies join forces to defeat the Ottoman Empire.
1762 – The Sultanate of Sulu ceded Balambangan Island to the British East India Company
1814 – Battle of North Point: an American detachment halts the British land advance to Baltimore in the War of 1812.
1846 – Elizabeth Barrett elopes with Robert Browning.
1847 – Mexican–American War: the Battle of Chapultepec begins.
1848 – A new constitution marks the establishment of Switzerland as a federal state.
1857 – The SS Central America sinks about 160 miles east of Cape Hatteras, North Carolina, drowning a total of 426 passengers and crew, including Captain William Lewis Herndon. The ship was carrying 13–15 tons of gold from the California Gold Rush.
1885 – Arbroath 36–0 Bon Accord, a world record scoreline in professional Association football.
1890 – Salisbury, Rhodesia, is founded.
1897 – Tirah Campaign: In the Battle of Saragarhi, ten thousand Pashtun tribesmen suffer several hundred casualties while attacking 21 Sikh soldiers in British service.
1906 – The Newport Transporter Bridge is opened in Newport, South Wales by Viscount Tredegar.
1910 – Premiere performance of Gustav Mahler's Symphony No. 8 in Munich (with a chorus of 852 singers and an orchestra of 171 players. Mahler's rehearsal assistant conductor was Bruno Walter)
1915 – French soldiers rescue over 4,000 Armenian Genocide survivors stranded on Musa Dagh.
1923 – Southern Rhodesia, today called Zimbabwe, is annexed by the United Kingdom.
1933 – Leó Szilárd, waiting for a red light on Southampton Row in Bloomsbury, conceives the idea of the nuclear chain reaction.
1938 – Adolf Hitler demands autonomy and self-determination for the Germans of the Sudetenland region of Czechoslovakia.
1940 – Cave paintings are discovered in Lascaux, France.
1940 – An explosion at the Hercules Powder Company plant in Kenvil, New Jersey kills 51 people and injures over 200.
1942 – World War II: RMS Laconia, carrying civilians, Allied soldiers and Italian POWs is torpedoed off the coast of West Africa and sinks with a heavy loss of life.
1942 – World War II: First day of the Battle of Edson's Ridge during the Guadalcanal Campaign. U.S. Marines protecting Henderson Field are attacked by Japanese troops.
1943 – World War II: Benito Mussolini is rescued from house arrest by German commando forces led by Otto Skorzeny.
1944 – World War II: The liberation of Yugoslavia from Axis occupation continues. Bajina Bašta in western Serbia is among the liberated cities.
1948 – Marshal Lin Biao, commander-in-chief of the Chinese communist Northeast Field Army, launched a massive offensive toward Jinzhou, Liaoshen Campaign has begun.
1952 – Strange occurrences, including a monster sighting, take place in Flatwoods, West Virginia.
1953 – U.S. Senator and future President John Fitzgerald Kennedy marries Jacqueline Lee Bouvier at St. Mary's Church in Newport, Rhode Island.
1958 – Jack Kilby demonstrates the first working integrated circuit while working at Texas Instruments.
1959 – The Soviet Union launches a large rocket, Lunik II, at the moon.
1959 – Bonanza premieres, the first regularly scheduled TV program presented in color.
1961 – The African and Malagasy Union is founded.
1962 – President Kennedy delivers his We choose to go to the Moon speech at Rice University.
1966 – Gemini 11, the penultimate mission of NASA's Gemini program, and the current human altitude record holder (except for the Apollo lunar missions)
1970 – Dawson's Field hijackings: Palestinian terrorists blow up three hijacked airliners in Jordan, continuing to hold the passengers hostage in various undisclosed locations in Amman.
1974 – Emperor Haile Selassie of Ethiopia, 'Messiah' of the Rastafari movement, is deposed following a military coup by the Derg, ending a reign of 58 years.
1974 – Juventude Africana Amílcar Cabral is founded in Guinea-Bissau.
1977 – South African anti-apartheid activist Steve Biko dies in police custody.
1980 – Military coup in Turkey.
1983 – A Wells Fargo depot in West Hartford, Connecticut, United States, is robbed of approximately US$7 million by Los Macheteros.
1983 – The USSR vetoes a United Nations Security Council Resolution deploring the Soviet destruction of Korean Air Lines Flight 007.
1984 – Dwight Gooden sets the baseball record for strikeouts in a season by a rookie with 246, previously set by Herb Score in 1954. Gooden's 276 strikeouts that season, pitched in 218 innings, set the current record.
1988 – Hurricane Gilbert devastates Jamaica; it turns towards Mexico's Yucatán Peninsula two days later, causing an estimated $5 billion in damage.
1990 – The two German states and the Four Powers sign the Treaty on the Final Settlement with Respect to Germany in Moscow, paving the way for German reunification.
1992 – NASA launches Space Shuttle Endeavour on STS-47 which marked the 50th shuttle mission. On board are Mae Carol Jemison, the first African-American woman in space, Mamoru Mohri, the first Japanese citizen to fly in a US spaceship, and Mark Lee and Jan Davis, the first married couple in space.
1992 – Abimael Guzmán, leader of the Shining Path, is captured by Peruvian special forces; shortly thereafter the rest of Shining Path's leadership fell as well.
1994 – Frank Eugene Corder fatally crashes a single-engine Cessna 150 into the White House's south lawn, striking the West wing. There were no other casualties.
2001 – Ansett Australia, Australia's first commercial interstate airline, collapses due to increased strain on the international airline industry, leaving 10,000 people unemployed.
2003 – The United Nations lifts sanctions against Libya after that country agreed to accept responsibility and recompense the families of victims in the 1988 bombing of Pan Am Flight 103.
2003 – Iraq War: In Fallujah, U.S. forces mistakenly shoot and kill eight Iraqi police officers.
2007 – Former Philippine President Joseph Estrada is convicted of plunder.
2008 – The 2008 Chatsworth train collision in Los Angeles between a Metrolink commuter train and a Union Pacific freight train kills 25 people.
2011 – The National September 11 Memorial & Museum in New York City opens to the public.
2014 – Three-year-old William Tyrrell disappears in Kendall, New South Wales, Australia
2015 – A series of explosions involving propane triggering nearby illegally stored mining detonators in the Indian town of Petlawad in the state of Madhya Pradesh(मध्य प्रदेश) kills at least 105 people with over 150 injured.
