The siege of Moscow in 1382 was motivated by khan Tokhtamysh's desire to punish Muscovy for its audacity to challenge the authority of the Golden Horde at the Battle of Kulikovo (1380).

[5] Tokhtamysh allied himself (in part through coercion) with the princes of Tver, Ryazan, and Nizhny Novgorod against Muscovy, and launched a surprise attack on the city in 1382.

And then, the pious prince [Dmitry Donskoy] came to an understanding and enlightenment, and after consideration, became perplexed and lost in thought, thereafter he became afraid to take a stand against the tsar [Tokhtamysh] himself.

[1][2] According to Crummey (1987, 2014), the besiegers lured Ostei out of the fortress under the pretense of seeking negotiations, killed him, and then broke into the Muscovite citadel, put many of its defenders to the sword, and destroyed large parts of Moscow city.

[2] Although Tokhtamysh did not deprive Donskoy of the title of grand prince of Vladimir, he did take his son Vasily hostage for several years (until he escaped upon his second attempt, and imposed a heavy tribute on all of Vladimir-Suzdalia).

[1][2] Kirpichnikov stated: "There is no dispute that Tokhtamysh's invasion of Moscow slowed the unification of the country and revived the separatism of some local rulers who rival the grand duke.