Crusaders capture and sack Constantinople, establishing the Latin Empire and permanently weakening Byzantium.
Date given in the Julian calendar.
A coalition of Christian Iberian kingdoms defeats the Almohads, a major turning point of the Reconquista.
King John of England seals Magna Carta at Runnymede, subjecting royal power to the law.
Richard the Lionheart and other European monarchs retake Acre but not Jerusalem; the Treaty of Jaffa with Saladin ends the campaign.
Mongol armies under Batu devastate the Rus' principalities and take Kiev in 1240, beginning over two centuries of Golden Horde domination.
During the Mongol invasion of Europe, Mongol forces defeat a Polish-led army in Silesia; two days later they rout the Hungarians at Mohi.
Mongol forces under Batu and Subutai rout the Hungarian army during the largest Mongol incursion into Europe.