In Europe, political strife and territorial disputes led to widespread warfare around the continent. England witnessed the Second Barons' War, a civil war fought over the aristocracy's disillusionment with King Henry III's attempts to maintain an absolute monarchy. The pope of the Catholic Church, aligned against the Hohenstaufen dynasty of the Holy Roman Emperor, succeeded in eliminating the line when the last male heir, Conradin, was killed by papal ally Charles I of Sicily, a Frenchman. Meanwhile, King Otakar II of Bohemia became the most powerful prince in Europe, expanding his territories through both warfare and inheritance. In other developments, both Iceland and Greenland accepted the overlordship of Norway, but Scotland was able to repulse a Norse invasion and broker a favorable peace settlement. In Spain, the Reconquista continued as several important cities were recaptured from the Moors. Political reforms were instituted in the election procedures of the pope and the doges of Venice, and the parliaments of Ireland and England met for the first time.
1263 - The chieftains of the eastern part of Iceland become the last to pledge fealty to the Norwegian king, bringing a more complete end to the Icelandic Commonwealth and the Icelandic civil war.
1265 - Before August - Future King Edward I escapes captivity in the hands of Simon de Montfort.
1265 - August 4 - The Battle of Evesham is fought in Worcestershire, with the army of Edward defeating the forces of rebellious barons led by Simon de Montfort and killing de Montfort and many of his allies. This is sometimes considered the death of chivalry in England.
1266 - October - The war winds down as supporters of the slain rebel leader Simon de Montfort make an offer of peace to the king in the Dictum of Kenilworth.
1267 - The Second Barons' War ends, as the rebels and King Henry III of England agree to peace terms as laid out in the Dictum of Kenilworth.
1264 to 1267 - The civil war in England known as the Second Barons' War marks a high point of struggle for political power between the landed aristocracy of England and the King.
1268 - New election procedures for the election of the doge are established in Venice in order to reduce the influence of powerful individual families.
1268 - Pope Clement IV dies; the following papal election fails to choose a new pope for almost three years, precipitating the later creation of stringent rules governing the electoral procedures.
1260 - September 3 - The Mongols are defeated by the Mamluks at the Battle of Ain Jalut in Palestine, marking the first decisive defeat of the Mongols and the point of maximum expansion of the Mongol Empire.
1266 - Niccolo and Maffeo Polo, brother and uncle of Marco Polo reach Kublai Khan's capital Khanbaliq (now Beijing) in China, setting the stage for Marco's famous expedition starting five years later. Kublai Khan sends the Polos back with a message requesting the pope dispatch western scholars to teach in the Mongol Empire; however, this request is largely ignored.
1268 - Kublai Khan sends an emissary to the Kamakura Shogunate of Japan demanding an acknowledgment of souzerainty and payment of tribute; the Japanese refuse, starting a diplomatic back-and-forth lasting until the Mongols attempt to invade in 1274.
1267 - Roger Bacon completes his work Opus Majus and sends it to Pope Clement IV, who had requested it be written; the work contains wide-ranging discussion of mathematics, optics, alchemy, astronomy, astrology, and other topics, and includes what some believe to be the first description of a magnifying glass. Bacon also completes Opus Minus, a summary of Opus Majus, later in the same year.
1268 - In France, the use of hops as the exclusive flavoring agent used in the manufacture of beer is made compulsory.
1260 - Germanmusical theoristFranco of Cologne publishes Ars Cantus Mensurabilis, in which he advances a new theory of musical notation in which the length of a musical note is denoted by the shape of that note, a system still used today.
1267 - The "Grand Capital" is constructed in Khanbaliq (present-day Beijing by Kublai Khan, having moved the capital of the Mongol Empire there three years prior.
1264 - King Boleslaus V of Poland promulgates legal protection for his Jewish subjects, including protection from the kidnapping and forcible baptism of Jewish children.
1264 - In Barcelona, a commission of Dominicans censors portions of the Talmud for the first time by ordering the cancellation of passages found reprehensible from a Christian point of view.
1267 - The leadership of Vienna forces Jews to wear Pileum cornutum,a cone-shaped head dress, in addition to the yellow badges Jews were already forced to wear.