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|1256 in poetry|
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- May 4 – Pope Alexander IV issues the papal bull Licet ecclesiae catholicae, constituting the Order of Saint Augustine at Lecceto Monastery.
- The city of Lviv, in present-day Ukraine, is founded by Danylo King of Rus.
- Theodore II Lascaris, Byzantine Emperor (in exile in the Empire of Nicaea), successfully concludes a military campaign started a year earlier, to recover Thrace from the Bulgarians.
- Abingdon School is founded in England.
- August 25: In Bologna slavery and serfdom is abolished; the event is recorded in the document called Liber Paradisus.
- Roger Bacon becomes a Franciscan friar.
- The Church of Santa Costanza, Rome, is consecrated.
- The ancient Irish Kingdom of Breifne splits into East Breifne and West Breifne, after a war between the O'Reillys and the O'Rourkes.
- The War of the Euboeote Succession begins, involving most of the lords of Frankish Greece and the Republic of Venice.
- June 30 – A large volcanic eruption in Harrat Rahat (near Medina) is associated with an Islamic prophecy.
- October – Mongol commander Baiju (operating under Hulagu Khan's command) leads his forces in a victory over Kay Ka'us II of the Sultanate of Rum, thereby capturing Anatolia.
- December 15 – Hulagu Khan captures and destroys the Hashshashin stronghold at Alamut in present-day Iran.
- Hulagu Khan establishes the Ilkhanate dynasty of Persia, which will become one of four main divisions of the Mongol Empire.
- The Japanese Kenchō era ends, and the Kōgen era begins.
- January 6 – Gertrude the Great, German mystic
- Robert, Count of Clermont, French founder of the House of Bourbon (d. 1317)
- Ibn al-Banna, Moroccan Arab mathematician (d. 1321)
- January 28 – William II, Count of Holland, King of Germany
- April 12 – Margaret of Bourbon, Queen of Navarre, regent of Navarre (b. c. 1217)
- June 13 – Tankei, Japanese sculptor (b. 1173)
- September 1 – Kujō Yoritsune, Japanese shogun (b. 1218)
- September 21 – William of Kilkenny, Lord Chancellor of England
- October 14 – Kujō Yoritsugu, Japanese shogun (b. 1239)
- Johannes de Sacrobosco, English scholar
- The Seismicity of Egypt, Arabia and the Red Sea: A Historical Review p. 40