The Chagatai Khanate had undergone a transformation after the Chagatayid Qazan Khan was killed in 1346.
In the west (Transoxiana), the mostly Turko-Mongol tribes, led by the Qara'unas amirs, have seized control.
In order to maintain a link to the house of Genghis Khan, the amirs have set several of his descendants on the throne, though these khans rule in name only and have no real power.
The eastern part of the khanate, meanwhile, has been largely autonomous for several years as a result of the khans' weakening power.
This eastern portion (most of which is known as "Moghulistan") is, in contrast to Transoxiana, primarily inhabited by Mongols and is largely Buddhist and Shamanist.
The most powerful family in the eastern part of the khanate during this time is a Mongol one, that of the Dughlat amirs.
The Dughlats hold several important towns as vassals to the khans, including Kashgar, Aksu, Yarkand, and Khotan.
The Dughlat amir Bulaji, after seeing the situation in Transoxiana, had decided in around 1347 to raise a khan of his own choosing.
His choice had fallen on Tughlugh Timur, who was at that time little more than an adventurer.
Tughlugh was converted by a Muslim cleric Mauláná Arshad-ud-Din, who unwittingly trespassed on the game-preserves of Tughlugh.
Tughlugh had ordered the cleric before him and demanded to know the reason for the cleric's interference with his hunting.
The cleric answered that he wasn't aware that he was trespassing.
At this point, Tughlugh noticed that the cleric was Persian, and Tughlugh said that "a dog was worth more than a Persian."
The cleric responded, "Yes, if we had not the true faith, we should indeed be worse than dogs."
Puzzled, Tughlugh ordered the cleric to explain the "true faith"; thus was Tughlugh taught the doctrines of Islam, whose concepts of ummah, ghazat (holy war), and jihad inspire his territorial expansionism into Transoxiana.
Thereafter, Tughlugh had embraced Islam.
The conversion is also politically convenient in that he brands the dissident princes which he kills as "heathens and idolaters".
This act results in the amirs of Moghulistan doing the same, although the general population of the region is slower in converting.