structural:scholar_edition, structural:reformatting
Mongol origins (1225–1241)

At his death in 1227, Genghis Khan divided the Mongol Empire amongst his four sons as appanages, but the Empire remained united under the supreme khan. Jochi was the eldest, but he died six months before Genghis. The westernmost lands occupied by the Mongols, which included what is today southern Russia and Kazakhstan, were given to Jochi's eldest sons, Batu Khan, who eventually became ruler of the Blue Horde, and Orda Khan, who became the leader of the White Horde. In 1235, Batu with the great general Subutai began an invasion westwards, first conquering the Bashkirs and then moving on to Volga Bulgaria in 1236. From there he conquered some of the southern steppes of present-day Ukraine in 1237, forcing many of the local Cumans to retreat westward. The Mongol campaign against the Kypchaks and Cumans had already started under Jochi and Subutai in 1216–1218 when the Merkits took shelter among them. By 1239 a large portion of Cumans were driven out of the Crimean peninsula, and it became one of the appanages of the Mongol Empire. The remnants of the Crimean Cumans survived in the Crimean mountains, and they would, in time, mix with other groups in the Crimea (including Greeks, Goths, and Mongols) to form the Crimean Tatar population. Moving north, Batu began the Mongol invasion of Rus' and spent three years subjugating the principalities, whilst his cousins Möngke, Kadan, and Güyük moved southwards into Alania.

Using the migration of the Cumans as their casus belli, the Mongols continued west, raiding Poland and Hungary, which culminated in Mongol victories at the battles of Legnica and Mohi. In 1241, however, Ögedei Khan died in the Mongolian homeland. Batu turned back from his siege of Vienna but did not return to Mongolia, rather opting to stay at the Volga River. His brother Orda returned to take part in the succession. The Mongol armies would never again travel so far west. In 1242, after retreating through Hungary, destroying Pest in the process, and subjugating Bulgaria, Batu established his capital at Sarai, commanding the lower stretch of the Volga River, on the site of the Khazar capital of Atil. Shortly before that, the younger brother of Batu and Orda, Shiban, was given his own enormous ulus east of the Ural Mountains along the Ob and Irtysh Rivers.

While the Mongolian language was undoubtedly in general use at the court of Batu, few Mongol texts written in the territory of the Golden Horde have survived, perhaps because of the prevalent general illiteracy. According to Grigor'ev, yarliq, or decrees of the Khans, were written in Mongol, then translated into the Cuman language. The existence of Arabic-Mongol and Persian-Mongol dictionaries dating from the middle of the 14th century and prepared for the use of the Egyptian Mamluk Sultanate suggests that there was a practical need for such works in the chancelleries handling correspondence with the Golden Horde. It is thus reasonable to conclude that letters received by the Mamluks – if not also written by them – must have been in Mongol.