[citation needed] The most important event during Dmitry's early reign was to start building the Moscow Kremlin; it was completed in 1367.

Other princes of in the northeastern Rus' principalities acknowledged his authority and contributed troops to the impending struggle against the Horde.

While he kept the Khan's patent to collect taxes for all of Russia,[citation needed] Dmitry is also famous for leading the first Russian military victory over the Mongols.

[citation needed] Mamai, a Mongol general and claimant to the throne, tried to punish Dmitry for attempting to increase his power.

Sergius sent the two warrior monks Alexander Peresvet and his friend Rodion Oslyabya to join the Russian troops.

[2] In gratitude for the victory, Dmitry established the Dormition monastery on the Dubenka River and built a church in honor of the Nativity of the Holy Theotokos over the graves of the fallen warriors.

Dmitry, however, pledged his loyalty to Tokhtamysh and to the Golden Horde and was reinstated as Mongol principal tax collector and Grand Duke of Vladimir.

They had at least twelve children: Right-Believing Prince Demetrius Ioannovich Donskoy was canonized on 6 June 1988 in Trinity Lavra of St. Sergius by 1988 Local Council of the Russian Orthodox Church under Patriarch Pimen I of Moscow.