1074: Reforming pope Gregory VII excommunicates married priests in a bid to impose strict clerical celibacy.
1862: 'Monitor' and 'Merrimack' clash in the American Civil War - the first ever battle between ironclad ships.
1945: United States bombers begin devastating 'firestorm raids' against Japan, which kill 250,000 people.
1862: 'Monitor' and 'Merrimack' clash in the American Civil War - the first ever battle between ironclad ships.
1945: United States bombers begin devastating 'firestorm raids' against Japan, which kill 250,000 people.