| 4 September 929 | Germany [wars] | A German army defeats the pagan Wends at Lenzen, on the River Elbe, and they are compelled to submit and accept Christianity. |
| 4 September 1260 | Sicily, Italy, Florence, Holy Roman Empire [political events] | King Manfred of Sicily's Sienese forces, under Count Jordan, defeat the Florentine Guelphs (anti-imperialists) at Montaperto, Italy. The city submits to a Ghibelline (imperialist) podestà (‘mayor’), Guido Novello. |
| 4 September 1479 | Castile, Spain, Portugal [treaties] | The Peace of Alcáçovas favours Isabella I, ending the succession struggle in Castile between Afonso V of Portugal and Ferdinand V and Isabella I, and Afonso tries to abdicate from the throne of Portugal. Under the agreement, the Atlantic islands are apportioned. The Canary Islands go to Castile, while Madeira, the Cape Verdes, and the Azores are retained by Portugal. |
| 4 September–6 November 1538 | India, Portugal, Ottoman Empire, Egypt [wars] | An Ottoman Egyptian fleet under Suleiman Pasha arrives to aid the Gujaratis in their blockade of the Portuguese-held fortress of Diu, northwest India; the Muslim admirals quarrel and the Egyptians return to Yemen, enabling the Portuguese to hold out. |
| 4 September 1543 | Ottoman Empire, Holy Roman Empire, Hungary [Habsburg–Ottoman Wars (1525–1718)] | Ottoman forces under Sultan Suleiman I the Magnificent assault and take the fortress of Székesfehérvár (Stuhlweissenberg), Hungary, southwest of Buda (now Budapest). The sultan returns to Constantinople, having strengthened the Danube frontier. |
| 4 September 1588 | England [births and deaths] | Robert Dudley, Earl of Leicester, favourite and suitor of Queen Elizabeth I of England, dies in Cornbury, Oxfordshire, England (c. 56). |
| 4 September 1870 | France [Franco–Prussian War (1870–71)] | The French defeat in the Franco-Prussian War leads to a revolt in Paris, France, against the government of Emperor Napoleon III. A provisional government of national defence is set up to continue the war against Prussia and a republic is proclaimed. |
| 4 September 1882 | USA [energy] | US inventor Thomas Alva Edison opens the Pearl Street electric generating station in New York City. The first in the USA, it employs three 125 horsepower steam generators to supply direct current (DC) to 225 houses. |
| 4 September 1883 | Russia, France [births and deaths] | Ivan Sergeyevich Turgenev, Russian novelist, poet, and playwright, dies in Bougival, near Paris, France (65). |
| 4 September 1886 | Ottoman Empire [political events] | King Alexander of Bulgaria abdicates following the coup and Stefan Nikolov Stambulov becomes regent. |
| 4 September 1907 | [births and deaths] | Edvard Grieg, Norwegian nationalist composer, dies in Bergen, Norway (64). |
| 4 September 1916 | German East Africa [World War I (1914–18)] | Allied troops under the South African general Jan Smuts take Dar es Salaam, the capital of German East Africa (now Tanzania). |
| 4 September 1940 | Romania [political events] | Ion Antonescu becomes prime minister of Romania and establishes a fascist dictatorship. King Carol II abdicates in favour of his son, Michael, and flees to Switzerland with his mistress, Magda Lupescu. |
| 4 September 1982 | UK [births and deaths] | Douglas Bader, British pilot who lost both legs in a flying accident, and went on to become an ace pilot in World War II, dies in London, England (72). |
