Siege of Moscow (1382)

After the death of Berdibeg, the Blue Horde fell into anarchy, with local khans in various places of the Horde's domains., Mamai Khan had emerged as a kingmaker in the political scenario of the Blue Horde. However, in 1380 Mamai was defeated by Dmitri Donskoi in the Battle of Kulikovo and was soon assassinated in Caffa.

However, 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 23 August, but his attack was beaten off by the Muscovites, who used firearms for the first time in Russian history. Three days later, two sons of supporter of Tokhtamysh, Dmitry of Suzdal, the dukes of Suzdal and Nizhny Novgorod Vasily and Semyon, who were present in Tokhtamysh's forces, 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.

The defeat reasserted the Horde's rule over some of Russian lands, which overthrew Tatar rule 98 years later by the great stand on the Ugra River. 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.