1243

By place

Europe

• March - King Ferdinand III turns the independent Taifa of Murcia into a protectorate, and initiates the process of the colonization and Christianization of the region. He receives the submission of the Moors, under the terms of a peace agreement.
• April 27 - Treaty of Bordeaux: King Louis IX and King Henry III agree to a truce that ends the Saintonge War. The truce does not stop the on-going clashes between France and England.
• Siege of Viterbo: Emperor Frederick II besieges Viterbo on request of the rebel citizens. The defenders are able to set fire to the siege towers and after signing a peace treaty, Frederick is persuaded to withdraw his army.
• Siege of Montségur: French forces begin the siege of Château de Montségur to raze the stronghold held by the rebellious Cathars. The castle is defended by some 100 troops and 500 refugees.
• May 1 - The Castillan troops are garrisoned in Murcia, to support the Hudid Dynasty.

England

• Spring - Henry III bestows the custody of Kenilworth Castle to Simon de Montfort. Simon's wife Eleanor, Henry's sister, already owned Odiham Castle so Simon has two of the strongest fortresses in England under his control.

Levant

• June 12 - A Crusader force under Balian III, lord of Beirut, captures Tyre after a long siege. The barons seize the citadel on July 10, with the help of Alice, queen of Cyprus, whose forces arrive on June 15. This ending the War of the Lombards.

Mongol Empire

• June 26 - Battle of Köse Dağ: The Mongols under Baiju Noyan defeat the Seljuk Turks of the Sultanate of Rum and their Byzantine allies. The Seljuks and the Empire of Trebizond become vassals of the Mongols.

By topic

Religion

• June 25 - Pope Innocent IV succeeds Celestine IV as the 180th pope of the Catholic Church, after a sede vacante of 7 months.