| 12 March 1088 | Holy Roman Empire [administration] | Cardinal Otto of Chatillon is elected as Pope Urban II at Terracina, near Gaeta, Naples, Rome being under the control of the Emperor Henry IV's antipope, Clement III. |
| 12 March 1144 | Papal States, Italy [administration] | Pope Lucius II is elected following the death of Pope Celestine II. |
| 12 March 1171 | Byzantine Empire, Venice, Italy [political events] | In an attempt to end Venetian dominance of trade in the Byzantine Empire, the emperor Manuel I Comnenus orders the arrest of all Venetians in the empire and the confiscation of their goods; Venice retaliates by attacking Dalmatia and the islands of Chios and Lesbos. |
| 12 March 1396 | France, England [treaties] | A treaty of truce for 28 years is made between France and England. Isabella, the daughter of King Charles VI of France, is betrothed to King Richard II of England. |
| 12 March 1689–3 July 1690 | UK [wars] | The dispossessed James II arrives at Kinsale in Ireland with French arms and assistance. In the space of a month he gains control of the entire country, with the exception of Londonderry and Enniskillen. |
| 12–15 March 1848 | Austrian Empire [revolution] | A revolution in Vienna, the Austrian capital, begins with demonstrations by liberal students, inspired by the revolutions in Paris, France, and Budapest, Hungary. |
| 12 March 1854 | UK, France, Ottoman Empire, Russian Empire [political events] | Britain and France conclude an alliance with the Ottoman Empire against Russia. |
| 12 March 1896 | Anglo-Egyptian Sudan, UK [wars] | In order to protect the Nile region from a French advance, Britain decides to undertake the re-conquest of Anglo-Egyptian Sudan, evacuated in 1885 because of the hostility of the Sudanese followers of the dervish Mahdi (prophet) Mohammed Ahmed of Dongola. |
| 12 March 1922 | Georgia, Armenia, Azerbaijan, RUSSIA [political events] | The communist republics of Georgia, Armenia, and Azerbaijan combine to form the Transcaucasian Socialist Republic. |
| 12 March 1925 | [births and deaths] | Sun Zhong Shan (Sun Yat-sen), leader of the Chinese Nationalist Party (Guomindang) which overthrew the Manchu dynasty, first president of the Republic of China 1911–12, and de facto ruler 1923–25, dies in Beijing, China (58). |
| 12 March–6 April 1930 | India [political events] | The Indian nationalist leader Mahatma Gandhi opens a civil-disobedience campaign in India with his ‘Salt March’ (a march from Ahmedabad, Gujarat, to Dandi on the coast where, on 6 April, Gandhi seizes salt to protest at the levying of salt tax on poor people). |
| 12 March 1933 | USA [political events] | President Roosevelt holds the first ‘fireside chat’ by radio with the US people, to encourage support for the New Deal. |
| 12 March 1938 | Austria, Germany [political events] | German troops are ordered to invade Austria to prevent a vote for continued independence in the referendum proposed by the Austrian chancellor Kurt von Schuschnigg; the referendum is called off before they enter Austrian territory. |
| 12 March 1940 | USSR, Finland [World War II (1939–45)] | The Russo-Finnish war ends. Finland signs a peace treaty with the USSR, ceding the Karelian Isthmus, the shores of Lake Ladoga, the city of Viborg, and the Hango naval base. 200,000 Finns are evicted from the area. |
| 12 March 1947 | USA, Greece, Turkey, USSR [diplomacy] | The US president Harry S Truman announces a plan (the Truman Doctrine) to give aid to Greece, which is threatened by communist insurrection, and to Turkey, which is under pressure from Soviet expansion. |
| 12 March 1955 | USA [births and deaths] | Charlie ‘Yardbird’ or ‘Bird’ Parker, US jazz saxophonist, composer, and bandleader, dies in New York City (34). |
| 12 March 1977 | Chile [law and government] | Political parties are banned in Chile and censorship is tightened under General Augusto Pinochet. |
| 12 March 1986 | Spain [political events] | Spain votes in a referendum to remain in NATO, but for its military forces to remain separate from the NATO command structure. |
| 12 March 1992 | Mauritius [decolonization] | Mauritius becomes a republic within the British Commonwealth. |
| 12 March 2000 | Italy [religion] | In a speech unprecedented for its sweeping apology, Pope John Paul II seeks forgiveness for the Catholic Church for 2000 years of violence against and persecution of Jews and other minority groups, and women. |
