Year 1237 (MCCXXXVII) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. Events By place Europe Summer – Emperor Frederick II assembles an expeditionary force (some 15,000 men) to crush the rebellious Lombard League. He crosses the Alps to Verona – where he is joined by Lord Ezzelino III da Romano, including troops from Brescia, Vicenza, Padua and Treviso. Frederick relies on his allies for support and in doing so, he provokes the opposition of earlier supporters, such as the House of Este, who now sides with the Lombards. August 15 – Battle of the Puig: Aragonese forces under Bernat Guillem de Montpeller defeat the Muslim army (some 12,000 men) of the Taifa of Valencia at El Puig. The Almohad forces are routed, and many of the soldiers are slain in the action. Zayyan ibn Mardanish, Almohad ruler and governor of Valencia, is forced to go into exile to Tunisia, while offering the surrender of all castles from the Turia River to Tortosa and Teruel. November 27 – Battle of Cortenuova: Frederick II defeats the forces of the Lombard League; about 5,000 Lombards are captured. Frederick makes a triumphal entry into the allied city of Cremona in the manner of an ancient Roman emperor, with the captured carroccio (later sent to the commune of Rome), and an elephant. During the winter campaign, Frederick captures the Piedmontese cities of Lodi, Novara, Vercelli, Chieri, and Savona. At the urging of King Louis IX (the Saint), Thomas II marries Joanna, widow of Ferdinand of Flanders, and daughter of the late Latin Emperor Baldwin I. Thomas becomes count of Flanders (or Jure uxoris). Livonian Crusade: The Livonian Brothers of the Sword are absorbed into the Teutonic Order, as the autonomous Livonian Order. An Estonian rebellion begins on Saaremaa Island (located in the Baltic Sea). England September 25 – Treaty of York: King Henry III signs an agreement with Alexander II at York. Alexander subjects to Henry's sovereignty and renounces the Scottish claims to Northumberland, Westmorland, and Cumberland. This establishes the Anglo-Scottish border in a form with the future status of several feudal properties and marks the end of Scotland's attempts to extend its frontier southward. Mongol Empire Autumn – Mongol invasion of Kievan Rus': The Mongol army commanded by Batu Khan and Subutai, invades the Principality of Ryazan (with representatives of all four khanates leading some