Year 1236 (MCCXXXVI) was a leap year starting on Tuesday (link will display the full calendar) of the Julian calendar. Events By place Byzantine Empire Spring – A fleet consisting of ships from the republics of Venice, Genoa and Pisa arrive at Constantinople. It is headed by Geoffrey II of Villehardouin, ruler of Achaea, who brings 100 of his own knights, 300 cross-bowman, and 500 archers. Geoffrey, formally a vassal of Emperor John I of Constantinople, breaks the blockade of the city, sinks 15 Byzantine ships and enters the Golden Horn. A treaty is signed for two years after the intervention of Angelo Sanudo, duke of Archipelago. Europe June 20 – Treaty of Kremmen: Duke Wartislaw III recognizes the seignory of Henry Borwin III, lord of Rostock, after his successful expedition against Wartislaw, in which he has conquered Circipania, including the cities of Gnoien and Kalen. Meanwhile, Duke Swietopelk II (the Great) conquers Schlawe and Stolp, the eastern part of Pomerania. To ease the tensions with Brandenburg, Wartislaw signs the Kremmen agreement. June – The 16-year-old Alexander Nevsky is elected by the Novgorodians as prince (knyaz) of Novgorod, beseeching the young Kievan noble to take charge of the city's military affairs. June 29 – Siege of Córdoba: Castilian forces under King Ferdinand III (the Saint) capture Muslim Córdoba from Emir Ibn Hud, as part of the Reconquista of the Iberian Peninsula. July – At a diet (princely convention) in Piacenza, Emperor Frederick II proclaims his wish to recover all Italy for the Holy Roman Empire. September 22 – Battle of Saule: The Lithuanians and Semigallians defeat the Livonian Brothers of the Sword, at Šiauliai in Lithuania. England January 14 – King Henry III marries the 14-year-old Eleanor of Provence, one of the four daughters of Raimond Berenguer, count of Provence. The ceremony takes place at Canterbury Cathedral, while Simon de Montfort, as Lord High Steward, takes care of the banquet and kitchen arrangements. Eleanor is crowned queen at Westminster Abbey shortly afterward. A tournament at Tickhill turns into a battle between northerners and southerners, but peace is restored by papal legate Otto of Tonengo. Mongol Empire The Mongols under Batu Khan, eldest of Jochi, sweep across Central Asia. They settle in the Russian steppe, curtailing the power of the Kievan Rus', extracting tribute from their neighbors, and disrupting their relationship with the Byzantine Empire. Autumn – Siege of Bilär: The