It is about the period from 1350 to 1400. One of the reasons for the aggravation was the weakening of the Golden Horde, there began a “great zamyat”, many khans were replaced, this disorganized the administration. In 1362, the troops of the Grand Duchy of Lithuania defeated the Horde in the Blue Waters region, and in 1376, 1378 and 1380 the Horde were defeated by Dmitry Donskoy.
Another reason can be considered the conflict in the Tver principality, it tried to get out of the influence of Moscow. The Moscow army in 1368 and 1370 made campaigns to Tver, and the Lithuanian prince Olgerd – to Moscow.
Finally, the third reason can be considered a religious issue. The metropolitan of the Russian lands was in Moscow since 1326, and Olgerd asked the patriarch from Constantinople to send a separate metropolitan for Kiev, Smolensk and other cities.
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