This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Islam becomes the state religion of the Golden Horde in two distinct steps that this atlas keeps separate rather than folding into a single date. The first came in 1252, when Berke, khan of the Golden Horde, personally converted to Islam at Bukhara, the first Mongol ruler of any of the successor khanates to do so. Berke's own conversion was a personal act of belief, carried by the khan himself, and it did not by itself make Islam the state's religion.
That second step waited nearly seventy years. Uzbeg Khan, ruling the Golden Horde in the early fourteenth century, proclaimed Islam the khanate's official state religion in 1321, converting the ruling institution itself rather than only its ruler. The gap between Berke's personal conversion in 1252 and Uzbeg's proclamation in 1321 is recorded here deliberately: one ruler's own belief and a state's declared religion are different facts, and collapsing them into a single moment would misstate how the change actually happened.
What this changed for Islam's spread was the conversion of one of the great Mongol successor states, ruling much of the Eurasian steppe and Russia's southern lands, from a religiously plural Mongol polity into an officially Islamic one, a shift with consequences for the Turkic and Mongol peoples under its rule for generations afterward.