| 27541 | March 12 | Event | 538 – Vitiges, king of the Ostrogoths ends his siege of Rome and retreats to Ravenna, leaving the city in the hands of the victorious Byzantine general, Belisarius. |
| 27542 | March 12 | Event | 1550 – Several hundred Spanish and indigenous troops under the command of Pedro de Valdivia defeat an army of 60,000 Mapuche at the Battle of Penco during the Arauco War in present-day Chile. |
| 27543 | March 12 | Event | 1622 – Ignatius of Loyola and Francis Xavier, founders of the Jesuits, are canonized as saints by the Catholic Church. |
| 27544 | March 12 | Event | 1689 – The Williamite War in Ireland begins. |
| 27545 | March 12 | Event | 1811 – Peninsular War: A day after a successful rearguard action, French Marshal Michel Ney once again successfully delayed the pursuing Anglo-Portuguese force at the Battle of Redinha. |
| 27546 | March 12 | Event | 1864 – American Civil War: The Red River Campaign begins as a US Navy fleet of 13 Ironclads and 7 Gunboats and other support ships enter the Red River. |
| 27547 | March 12 | Event | 1868 – Henry O'Farrell attempts to assassinate Prince Alfred, Duke of Edinburgh. |
| 27548 | March 12 | Event | 1868 – Basutoland, toaday called Lesotho is annexed by the United Kingdom. |
| 27549 | March 12 | Event | 1881 – Andrew Watson makes his Scotland debut as the world's first black international football player and captain. |
| 27550 | March 12 | Event | 1885 – Tonkin Campaign: France captures the citadel of Bắc Ninh. |
| 27551 | March 12 | Event | 1894 – Coca-Cola is bottled and sold for the first time in Vicksburg, Mississippi, by local soda fountain operator Joseph Biedenharn. |
| 27552 | March 12 | Event | 1910 – Greek cruiser Georgios Averof is launched at Livorno. |
| 27553 | March 12 | Event | 1912 – The Girl Guides (later renamed the Girl Scouts of the USA) are founded in the United States. |
| 27554 | March 12 | Event | 1913 – Canberra Day: The future capital of Australia is officially named Canberra. (Melbourne remains temporary capital until 1927 while the new capital is still under construction.) |
| 27555 | March 12 | Event | 1918 – Moscow becomes the capital of Russia again after Saint Petersburg held this status for 215 years. |
| 27556 | March 12 | Event | 1920 – The Kapp Putsch begins when the Marinebrigade Ehrhardt is ordered to march on Berlin. |
| 27557 | March 12 | Event | 1921 – İstiklâl Marşı is adopted in the Grand National Assembly of Turkey. |
| 27558 | March 12 | Event | 1922 – Armenia, Georgia and Azerbaijan form The Transcaucasian Socialist Federative Soviet Republic |
| 27559 | March 12 | Event | 1928 – In California, the St. Francis Dam fails the resulting floods kill over 600 people. |
| 27560 | March 12 | Event | 1930 – Mahatma Gandhi leads a 200-mile march, known as the Salt March, to the sea in defiance of British opposition, to protest the British monopoly on salt |
| 27561 | March 12 | Event | 1933 – Great Depression: Franklin D. Roosevelt addresses the nation for the first time as President of the United States. This is also the first of his "fireside chats". |
| 27562 | March 12 | Event | 1934 – Konstantin Päts and General Johan Laidoner stage a coup in Estonia, and ban all political parties. |
| 27563 | March 12 | Event | 1938 – Anschluss: German troops occupy and absorb Austria. |
| 27564 | March 12 | Event | 1940 – Winter War: Finland signs the Moscow Peace Treaty with the Soviet Union, ceding almost all of Finnish Karelia. Finnish troops and the remaining population are immediately evacuated. |
| 27565 | March 12 | Event | 1942 – Pacific War: The Battle of Java ends with an Allied surrender to the Japanese Empire. |
| 27566 | March 12 | Event | 1947 – The Truman Doctrine is proclaimed to help stem the spread of Communism. |
| 27567 | March 12 | Event | 1950 – The Llandow air disaster occurs near Sigingstone, Wales, in which 80 people die when their aircraft crashed, making it the world's deadliest air disaster at the time. |
| 27568 | March 12 | Event | 1961 – First winter ascent of the North Face of the Eiger. |
| 27569 | March 12 | Event | 1967 – Suharto takes over from Sukarno to become Acting President of Indonesia. |
| 27570 | March 12 | Event | 1968 – Mauritius achieves independence from the United Kingdom. |