Saint Dmitry Ivanovich Donskoi (Дми́трий Донско́й), or Dimitri of the Don, sometimes referred to as Dmitry I (October 12, 1350, Moscow – May 19, 1389, Moscow), son of Ivan II Krasnyi, reigned as the Prince of Moscow from 1359 and Grand Prince of Vladimir from 1363 to his death. He was the first prince of Moscow to openly challenge Tatar authority in Russia. His nickname, Donskoi (i.e., "of the Don"), alludes to his great victory against the Tatars in the Battle of Kulikovo (1380) which took place on the Don River.
The most important event during the early years of Dmitri's reign was construction of the first stone Moscow Kremlin, completed in 1367. The new fortress allowed the city to withstand two sieges by Algirdas of Lithuania, in 1368 and 1370. Attempt for the third siege in 1372 ended in Treaty of Lyubutsk. In 1375, Dmitri managed to settle his conflict with Mikhail II of Tver over Vladimir in his favour. Other princes of Northern Russia also acknowledged his authority and contributed their troops to his impending struggle against the Horde. By the end of his reign, Dmitri more than doubled territory of Moscow principality.
Dmitri's thirty-year reign saw the beginning of the end for Mongol domination of parts of what is now Russia. The Golden Horde was severely weakened by civil war and dynastic rivalries. Dmitri took advantage of this lapse in Mongol authority to openly challenge the Tatars.
While he kept the Khan's patent to collect taxes for all of Russia, Dmitri is also famous for leading the first Russian military victory over the Mongols. Mamai, a Mongol general and claimant to the throne, tried to punish Dmitri for attempting to increase his power. In 1378 Mamai sent a Mongol army, but it was defeated by Dmitri's forces in the Battle of Vozha River Two years later Mamai personally led a large force against Moscow. Dmitri met and defeated it at the Battle of Kulikovo.
The defeated Mamai was presently dethroned by a rival Mongol general, Tokhtamysh. That khan reasserted Mongol rule over parts of what now is Russia and overran Moscow for Dmitri's resistance to Mamai. Dmitri, however, pledged his loyalty to Tokhtamysh and to the Golden Horde and was reinstated as Mongol principal tax collector and Grand Duke of Vladimir. Upon his death in 1389, Dmitri was the first Grand Duke to bequeath his titles to his son Vasili without consulting the Khan.