| 12 August 1549 | England, France [wars] | Following King Henry II of France's declaration of war on England on 8 August, his forces capture Ambleteuse Castle, between Calais and Boulogne in northern France, besieging the latter. |
| 12 August 1641 | UK [treaties] | King Charles I of Great Britain and Ireland signs the Treaty of London with Scotland, an agreement which ratifies the 1640 Treaty of Berwick.Two days later he departs for Scotland to try to gain the support of the Covenanters against the English Parliament. |
| 12 August 1687 | Hungary, Holy Roman Empire, Ottoman Empire [wars] | Imperial forces under Charles, Duke of Lorraine, unexpectedly defeat an Ottoman army, led by Süleyman Pasha, at Nagyharsány (Berg Hasan), near Mohács. For the first time in 150 years Hungary is free from Ottoman influence. |
| 12 August 1711 | Russia, Ottoman Empire, Sweden [Ottoman–Russian Wars (1686–1739)] | The Russian Tsar Peter I the Great, surrounded by a much larger Ottoman army on the River Prut in Moldavia, makes peace with the Ottoman Empire. The Black Sea fortress of Azov and fortress and harbour of Taganrog are to be returned to Ottoman control. Russia is to withdraw from the Black Sea and to demolish its forts on the lower River Dnieper. Russian troops are also to evacuate Poland, and King Charles XII, a guest of Sultan Ahmed III following his defeat at the battle of Poltava, is granted free passage home to Sweden. |
| 12 August 1828 | England [births and deaths] | William Blake, English poet and engraver, dies in London, England (70). |
| 12 August 1848 | England [births and deaths] | George Stephenson, English engineer, inventor of the railway locomotive, dies in Chesterfield, Derbyshire, England (67). |
| 12 August 1851 | USA [tools] | US inventor Isaac Merrit Singer patents the first practical domestic sewing machine for general use, in Boston, Massachusetts. His design, which enables continuous and curved stitching, and allows any part of the material to be worked on, sets the pattern for all subsequent sewing machines. |
| 12 August 1858 | Canada [telephone services] | The first message by transatlantic telegraph cable is sent from Newfoundland, Canada, to Valentia, Ireland. |
| 12 August 1873 | Russian Empire, Central Asia [colonization] | Russia assumes suzerainty of the Khanates of Khiva and Bukhara, pushing further into central Asia. |
| 12 August 1881 | USA [births and deaths] | Cecil B de Mille, US motion picture director and producer known for his spectacular films, born in Ashfield, Massachusetts (–1959). |
| 12 August 1887 | Austria [births and deaths] | Erwin Schrödinger, Austrian physicist who develops the wave theory of matter, born in Vienna, Austria (–1961). |
| 12 August 1898 | Pacific, USA [colonization] | The islands of Hawaii are annexed to the USA. |
| 12 August 1908 | USA [motor vehicles] | US car manufacturer Henry Ford of the Ford Motor Company introduces the Model T. Inexpensive (sold for $850), easy to maintain, and mass-produced after 1913, it revolutionizes transportation. |
| 12 August 1922 | [births and deaths] | Arthur Griffith, Irish journalist and nationalist, founder of Sinn Fein 1905, president of the Dáil of the Irish Free State (now the Republic of Ireland) 1922, dies suddenly of a brain haemorrhage, in Dublin, Ireland (60). |
| 12 August 1957 | British Guiana [elections] | Following Britain's decision to restore self-government in British Guiana (now Guyana), an election is held for 14 seats on a new legislative council. Cheddi Jagan's People's Progressive Party wins 9 seats and, on 15 August, Jagan forms a government. |
| 12 August 1972 | North Vietnam, South Vietnam, USA [Vietnam War (1954–75)] | Heavy US air raids on North Vietnam accompany the departure of US combat infantry from South Vietnam. |
| 12–14 August 1974 | Turkey [political events] | Turkey issues a 24-hour ultimatum demanding the creation of autonomous Turkish cantons in Cyprus. On 14 August, Turkish forces resume their offensive having turned down appeals by Greek foreign minister George Manos and Cypriot president Nicos Sampson to consult their governments. |
| 12 August 1975 | New Zealand, Sweden [athletics] | John Walker of New Zealand becomes the first man to run a mile in under 3 minutes 50 seconds, in Gothenburg, Sweden. |
| 12 August 1981 | USA [computing] | IBM launches its personal computer, using the Microsoft disk-operating system (MS-DOS). |
