The Hungarian Civil War of 1264–1265 () was a brief dynastic conflict between King Béla IV of Hungary and his son Duke Stephen at the turn of 1264 into 1265.
Béla's relationship with his oldest son and heir, Stephen, became tense in the early 1260s, because the elderly king favored his daughter Anna and his youngest child, Béla, Duke of Slavonia. Stephen accused Béla of planning to disinherit him. After a brief skirmish, Stephen forced his father to cede all the Kingdom of Hungary's lands east of the Danube to him and adopted the title of junior king in 1262. Nevertheless, their relationship remained tense, causing a civil war by the end of 1264. The conflict resulted in Stephen's victory over his father's royal army. They concluded a peace treaty in 1266, which failed to restore confidence between them. Béla died in 1270. The 1264–1265 civil war was one trigger for the emerging feudal anarchy in Hungary by the last decades of the 13th century.
Sources seldom mention the civil war. Letters of donation and superficial hints from Hungary, Austrian chronicles and annales briefly record some events without context. Consequently there are several historiographical reconstructions of the chronology of the civil war. This article follows the most accepted reconstruction of the events compiled by historian Attila Zsoldos in his work, the only monograph about the conflict between Béla IV and Stephen.
Background
Social changes
When Béla IV ascended the Hungarian throne in 1235, he declared his principal purpose was "the restitution of royal rights" and "the restoration of the situation which existed in the country" during the reign of his grandfather, Béla III. He set up special commissions, which revised all royal charters of land grants made after 1196. The monarch's annulment of former donations alienated many of his subjects from him.
The First Mongol invasion of Hungary (1241–1242) devastated much of the Kingdom of Hungary. This devastation was especially heavy in the plains east of the Danube, where at least half of the villages were depopulated. Preparation for a new Mongol invasion was the central concern of Béla's policy. In a 1247 letter to Pope Innocent IV, Béla announced his plan to strengthen the Danube with new forts. He abandoned the ancient royal prerogative to build and own castles, promoting the construction of nearly 100 new fortresses by the end of his reign. Béla made land grants in the forested regions. In return, the new landowners were obliged to equip heavily armoured cavalrymen to serve in the royal army. To replace those who perished during the Mongol invasion, Béla IV promoted colonisation. Germans, Moravians, Poles, Ruthenians and other "guests" arrived from neighbouring countries and were settled in depopulated or sparsely populated regions. He also persuaded the Cumans, who left Hungary in 1241, to return and settle on the plains along the river Tisza.
Tense relationship
King Béla's eldest son Stephen was born in 1239. A royal charter of 1246 mentions Stephen as "King, and Duke of Slavonia". Apparently, in the previous year, Béla had his son crowned as king, proclaiming him as his heir apparent. He endowed Stephen with the lands between the river Drava and the Adriatic Sea. Since 1245, young Stephen nominally ruled the provinces of Croatia, Dalmatia and Slavonia. When Stephen attained the age of majority in 1257, his father appointed him Duke of Transylvania. Stephen's rule there was short-lived, because his father transferred him to Styria in 1258. His rule remained unpopular in Styria. With support from King Ottokar II of Bohemia, the local lords rebelled against the Hungarian administration. Although Stephen achieved important successes during the war in Bohemia, in the decisive Battle of Kressenbrunn King Béla's and Stephen's united army was vanquished on 12 July 1260, primarily because the main forces under Béla's command arrived late. Stephen, who commanded the advance guard, barely escaped from the battlefield. The Peace of Vienna, which was signed on 31 March 1261, ended the conflict between Hungary and Bohemia, forcing Béla IV to renounce of Styria in favour of Ottokar II. Stephen returned to Transylvania and ruled it for the second time after their departure from Styria.