February 10–Siege of Baghdad: Mongol forces (some 150,000 men), led by Hulagu Khan, besiege and conquer Baghdad after a siege of 13 days. During the first week of February, the eastern walls begin to collapse, and the Mongols swarm into the city, on February 10. Caliph Al-Musta'sim surrenders himself to Hulagu – together with all the Abbasid chief officers and officials. They are ordered to lay down their arms, and are massacred. Hulagu imprisons Al-Musta'sim among his treasures, to starve him to death. Meanwhile, massacres continue throughout the whole city; in 40 days about 80,000 citizens are murdered. The only survivors are the ones who are hiding in cellars which are not discovered, and a number of attractive girls and boys who are kept to be slaves, and the Christian community, who take refuge in the churches which are left undisturbed, by the special orders of Hulagu's wife, Doquz Khatun.[1]
February 15– Hulagu Khan enters Baghdad, where many quarters of the city are ruined by fire. The Great Library (or House of Wisdom) is destroyed, numerous precious book collections are thrown into the Tigris River. Before the siege, about 400,000 manuscripts are rescued by Nasir al-Din al-Tusi, Persian polymath and theologian, who takes them to Maragheh (located in East Azerbaijan Province). The sack of Baghdad brings an end to the Abbasid Caliphate (750-1258) and the Islamic Golden Age. Many professors, physicians, scientists, clerics, artists and lecturers are also massacred.
August 25– George Mouzalon is assassinated in Magnesia ad Sipylum, as part of a conspiracy led by Byzantine nobles, under future Emperor Michael VIII (Palaiologos).
May 2 – King Henry III accepts the demand of Simon de Montfort and his baronial supporters that the government is reformed with a committee of 22 barons, including the king. As an act of faith, Simon de Montfort hands over his estates at Odiham and Kenilworth as part of the proposals. The Provisions of Oxford establish baronial control of the government, also known as the Oxford Parliament, on June 11.[3][4]
June 25–Battle of Acre: The Genoese send an armada (some 50 galleys) to relieve the blockade at Acre and ask for the assistance of Philip of Montfort, lord of Tyre, and the Knights Hospitaller for a combined attack from the land side. The Genoese fleet's arrival takes the Venetians by surprise but the superior experience and seamanship result in a crushing Venetian victory, with half the Genoese ships lost. Later, the Genoese garrison is forced to abandon Acre.[5][6]
Asia
Mongol invasions of Vietnam: Mongol forces (some 30,000 men) under Uriyangkhadai, son of Subutai, invade Vietnam. After many battles, the Vietnam army is routed and defeated. The senior leaders are able to escape on pre-prepared boats, while the remnants are destroyed on the banks of the Red River. The Mongols occupy the capital city, Thăng Long (modern-day Hanoi), and massacres the city's inhabitants, by the end of January.[7]
Fine, John Van Antwerp (1994). The Late Medieval Balkans: A Critical Survey from the Late Twelfth Century to the Ottoman Conquest, p. 161. Ann Arbor, Michigan: University of Michigan Press. ISBN0-472-08260-4.
Stothers, R. B. (2000). "Climatic and Demographic consequences of the massive volcanic eruption of 1258". Climatic Change. 45 (2): 361–374. doi:10.1023/A:1005523330643. S2CID42314185.