In 1378, Tokhtamysh, a descendant of Orda Khan and an ally of Tamerlane, assumed the power in the White Horde and annexed Blue Horde by fording across the Volga and quickly annihilated an army sent by Muscovy. He then united the hordes and formed the Golden Horde.

After uniting the two hordes, Tokhtamysh promoted a military campaign to restore the Tatar power in Russia. After ravaging some small cities, he besieged Moscow on the 23rd of August, but his attack was beaten off by the Muscovites, who used firearms for the first time in Russian history. Three days later, the two sons of Dmitry of Suzdal, who was a supporter of Tokhtamysh, present at the siege, namely the dukes of Suzdal and Nizhny Novgorod Vasily and Semyon, persuaded Muscovites to open the city gates, promising that forces would not harm the city in this case. That allowed Tokhtamysh's troops to burst in and to ravage Moscow, killing around 24,000 people in the process.

The defeat reasserted the Horde's rule over some of Russian lands. Tokhtamysh also re-established the Golden Horde as a dominant regional power, reunified the Mongol lands from Crimea to Lake Balkash and defeated Lithuanians at Poltava in the next year. However, he made the disastrous decision to wage a war against his former master, Tamerlane, and the Golden Horde never recovered.