| 20 March 43 BC | Roman Empire [births and deaths] | Ovid, Roman poet known for his poem ‘Ars amatoria’/‘Art of Love’, born in Sulmo, Roman Empire (–AD 18). |
| 20 March 1239 | Holy Roman Empire, Bavaria, Bohemia, Germany [political events] | Pope Gregory IX excommunicates the Holy Roman Emperor Frederick II for infringing the church's rights in Italy. In Germany, only Bavaria and Bohemia rebel in consequence. |
| 20 March 1413 | England [political events] | Henry V succeeds to the English throne following the death of his father, King Henry IV of England. |
| 20 March 1413 | England [births and deaths] | Henry IV, king of England 1399–1413, son of John of Gaunt, dies in London, England (46). |
| 20 March 1598 | France [treaties] | By the Treaty of Ponts-de-Cé, Philippe-Emmanuel, Duke of Mercoeur, leader of the Catholic League in Brittany, submits to King Henry IV of France for 4 million livres and the hand of Henry's illegitimate son, the Duke of Vendôme for his daughter, ending French Catholic resistance to Henry IV. |
| 20 March 1619 | Holy Roman Empire [political events] | The Holy Roman Emperor Matthias II dies; his heir, Archduke Ferdinand of Styria, King of Bohemia, King of Hungary, is formally elected as Matthias's successor in August. |
| 20 March 1727 | England [births and deaths] | Isaac Newton, English physicist and mathematician who laid the foundations of calculus and gravitation theory, dies in London, England (84). |
| 20 March 1816 | Portugal [political events] | Maria I, the insane queen of Portugal, dies. She is succeeded by her son, John VI. |
| 20 March 1828 | Norway [births and deaths] | Henrik Johan Ibsen, Norwegian poet and playwright whose works include Peer Gynt (1867) and A Doll's House (1879), born in Skien, Norway (–1906). |
| 20 March 1848 | India, UK [wars] | The Second Anglo-Sikh War begins in India, arising out of the Sikh aristocracy's discontent at British administration and the subsequent murder of two British officers. |
| 20 March 1890 | Germany [law and government] | Otto von Bismarck is dismissed by the new emperor Wilhelm II and Leo, Count von Caprivi, becomes German chancellor. |
| 20 March 1934 | Germany [technology] | German scientist Rudolf Kuhnold, using a 700-watt transmitter on 600 megacycles plus a receiver, succeeds in receiving echoes bounced off a battleship anchored 550 m/1,800 ft away. It is the first practical demonstration of radar. |
| 20 March 1977 | India [elections] | The Congress Party is defeated in the Indian general election and the prime minister Indira Gandhi loses her seat. |
| 20 March 1990 | UK [television] | The chancellor of the Exchequer's budget is televised for the first time in Britain. |
| 20 March 1993 | Bosnia-Herzegovina [Balkan conflicts (c. 1991–2000)] | The United Nations (UN) supervises the evacuation of civilians from the Muslim enclave of Srebrenica in Bosnia-Herzegovina, besieged for almost a year (the siege ends on 18 April). |
| 20–31 March 2003 | Iraq [Second Gulf War (2003)] | Despite inconclusive inspections for weapons of mass destruction and failure to win United Nations Security Council backing for military action to forcefully disarm Saddam Hussein's regime in Iraq, the USA and UK launch air strikes on Iraqi strategic targets, particularly in the capital Baghdad. French and German opposition to the action causes serious friction in the Western alliance, and Russia similarly expresses dissent. By the end of March, as the Iraqi government remains defiant and reports of increasing civilian casualties provoke worldwide concern, US ground forces from bases in the Gulf advance on Baghdad to confront the elite troops of the Iraqi Republican Guard. Meanwhile, British forces surround Iraq's second city of Basra in the south of the country. |
