Sartaq had been succeeded briefly by Ulaqchi, before his uncle Berke, Batu Khan’s brother, succeeds to the throne as the second khan of the Blue Horde. (It is not clear whether Ulaqchi had been his brother or his son.)

Following the destruction of the Abbasid caliphate by the Il-Khanid Mongols, the Mamluks conclude a treaty with Berke, who is a recently converted Muslim.

Béla had had his eldest son, Stephen crowned junior king already in 1246, but he did not want to share the royal power with his son.

However, Stephen recruits an army against his father and in 1258 persuades Béla to cede him the government of Transylvania, which had been among the territories devastated by the Golden Horde during the Mongol invasion of Europe in 1241-1242, during which a large portion of the population had perished.

In the same year, the Styrians, who would have preferred the rule of the King of Bohemia, rise against Béla's reign, but his troops suppress their rebellion.

After his victory, Béla appoints his son Duke of Styria.

The Hungarian kingdom has occupied the Bulgarian province of Belgrade.

Cuman domination over Wallachia had ended in 1241 during the Mongol invasion of Europe.

A direct Mongol rule over Wallachia is not attested, but it remains probable.

Part of Wallachia had probably been briefly disputed by the Hungarian Kingdom and Bulgarians in the following period, but it appears that the severe weakening of Hungarian authority during the Mongol attacks has contributed to the establishment of the new and stronger polities attested in Wallachia for the following decades.

Bulgaria has gradually lost control and traditional significant political influence over Wallachia, where the power of the regional nobles has grown stronger.

(Local principalities will subsequently be established.)

The population of Baghdad had grown to between three hundred thousand and five hundred thousand by the tenth century.

The great city’s early meteoric growth had slowed due to troubles within the 'Abbasid Caliphate, including relocations of the capital to Samarra (during 808–819 and 836–892), the loss of the western and easternmost provinces, and periods of political domination by the Iranian Buwayhids (945–1055) and Seljuq Turks (1055–1135).

Nevertheless, the city remains one of the cultural, educational, and commercial hubs of the Islamic world and the capital of the Caliphate.

The Mongols have laid siege to the city from three sides.

'Abbasid caliph al-Musta'sim, ineffectual himself and surrounded by advisers with conflicting opinions, presents no strong defense against the southern wing of the Mongols, whose program is to subdue the Islamic world.

Al-Musta'sim ignores several demands by Hulagu and answers others with blustering and empty threats.

On January 30, 1258, Hulagu orders the bombardment of Baghdad.

Baghdad’s defenses are ruined within three days, while Mongol engineers are destroying the irrigation dikes to flood the city and drown the defenders.

The caliph and three hundred officials hurry to present their surrender and, ten days later, are all executed, Musta'sim and all but one of his sons by being rolled in carpets and trampled to death by horses.

The sole surviving son is sent to Mongolia.

This leaves Islam without a caliph for the first time in its history, a blow from which Islamic civilization will never fully recover.

After securing the city’s defeat on February 10, 1258, the Mongols loot the city and burn it to the ground.

The survivors are then assembled on the plain outside the city, where they are shot and hacked to death, their corpses piled in heaps.

Over a period of days, between ninety thousand and one million men, women and children are slain in a mass slaughter of all the inhabitants except Christians, themselves spared by the intervention of Hulagu’s Nestorian Christian wife Dokuz Khatun.

Baghdad, its dikes destroyed and its irrigation canals filled in by the Mongols and no citizens left to restore it, is to remain a depopulated, ruined city for several centuries and will only gradually recover some of its former glory.

The Muslim states of Syria are caught in the middle of the contest between the Mongols and the Mamluks, and the Latin states are in grave danger.

Hethum continues as a vassal of the Mongols; his son-in-law, …

…Bohemond VI of Antioch-Tripoli, a principality increasingly aloof and through intermarriage closely tied to Armenia, follows suit.

Nicaea’s war over Bulgaria’s disintegrating empire is still being waged at the time of Theodore's death at 36, in August 1258.

His eight-year-old son by Helen, a daughter of the late Bulgarian tsar Ivan Asen II, succeeds him as John IV.

His regent George Muzalon, a trusted friend of the former emperor, advises John but Muzalon is assassinated nine days after Theodore's death by associates of Michael Palaiologos, who now becomes regent, together with the patriarch Arsenios.