Year 1264 (MCCLXIV) was a leap year starting on Tuesday (link will display the full calendar) of the Julian calendar.
Events
By place
Byzantine Empire
Spring – Battle of Makryplagi: Constantine Palaiologos, half-brother of Emperor Michael III (Palaiologos), resumes operations against the Principality of Achaea. He advances up in northern Elis, and sets up his camp at a location called "St. Nicholas of Mesiskli". Prince William II of Villehardouin with his own troops march to meet him and arrays his men ready for battle. The Byzantine vanguard under Michael Kantakouzenos, ride forth from the Byzantine lines, but the force is ambushed and Michael is killed by the Achaeans. Constantine retreats and goes on to lay siege to the fortress of Nikli. There, Turkish mercenaries (some 1,000 horsemen), confront him and demand that he pay them their arrears of 6 months. Constantine refuses, whereupon the Turkish troops desert to William. He decides to raise the siege and departs for Constantinople. He leaves Alexios Philes with a force and marches towards Messenia, where he occupies the passes, situated near Gardiki Castle. William, reinforced by the Turkish contingent, marches to Messenia to attack the Byzantines, despite their holding strong positions on the high ground. The first two attacks are beaten off, but during the third attack, the Byzantines flee in panic. Alexios, along with many Greek nobles, are captured.
Europe
January 23 – King Louis IX (the Saint) issues the Mise of Amiens, a settlement between King Henry III and his rebellious barons under Simon de Montfort, heavily favouring the former – which leads to the Second Barons' War. At Amiens, Henry accuses the barons of destroying his castles and laying waste to royal lands. For this he demands a compensation of some £300,000 and 200,000 marks, which is defended by Louis. August – Mudéjar Revolt: Muslim rebel forces, aided by allies from Algeciras and Tarifa, take the town of Jerez de la Frontera after defeating the outnumbered Castilian garrison led by Nuño González de Lara (the Good). The rebels are supported by Muhammad I, ruler of the Emirate of Granada, while King Alfonso X (the Wise) is allied with Aragon. The rebels manage to capture Murcia, as well as several smaller towns. August 14 – Battle of Saseno: The Genoese fleet (16 galleys) manages to trick and capture an entire Venetian trade convoy near Saseno Island off the coast of Albania. The captured merchandise and ships are valued at more than 100,000 Genoese pounds, an enormous sum for the period, of which 30,000 goes into the Genoese treasury through the sale of the plunder. October 9 – Castilian forces under Alfonso X (the Wise) counter-attack and recapture Jerez de la Frontera, after a siege. The rebel-held towns of Vejer de la Frontera, Rota, and Sanlúcar de Barrameda also fall to Alfonso. Muslims in the retaken towns are expelled and the mosques in Jerez are converted to churches. The region is settled by Christians from elsewhere.Harvey, L. P. (1992). Islamic Spain, 1250 to 1500, p. 54. Chicago: University of Chicago Press. . December 10 – Hungarian Civil War: A dynastic conflict erupts between King Béla IV and his son, Duke Stephen. Hungarian forces under Ladislaus II Kán invades Stephen's realm and push forward unhindered penetrating the valley of the Mureș River in the southern part of Transylvania. Stephen's army halts Ladislaus' advance at the Fortress of Deva (modern Romania). Winter – The War of the Thuringian Succession ends after 17 years with the state of Hesse gaining its independence from Thuringia and becoming the Landgraviate of Hesse, a principality of the Holy Roman Empire. High Duke Bolesław V (the Chaste) promulgates legal protection for Jewish communities in Lesser Poland, including protection from kidnapping and forcible baptism of Jewish children (approximate date).