Russia was united against the Mongol; all the dukes, with the exception of those of Tver and Riazan, lent their aid. These two dreaded Moscow's power, and the Duke of Riazan tried to conclude an alliance with Jagellon of Lithuania and Mamaï.
Dmitri, at the head of an army estimated at 150,000 men, marched through Riazan to the Don where the Tartars were drawn up, awaiting the reinforcements of their ally Jagellon, who was still fifteen leagues distant. Dmitri resolved to fight the Tartars before a junction could be effected. He crossed the Don and met the enemy on the plain of Koulikovo,—the Field of the Woodcocks,—where a furious battle was fought. It was decided by a sudden attack upon the Tartars from an ambush, which threw them into a panic. The Tartars were routed; Mamaï's camp, his chariots and camels, were all captured. Dmitri was found in a swoon from loss of blood. He was surnamed Donskoï, in honor of this victory. (1380.)
It seemed as if the end of the Mongol yoke had come, when another great leader appeared among them. Tamerlane, after conquering Bokhara, Hindostan, Iran, and Asia Minor, entered Europe, and ordered Mamaï to be put to death. He summoned Dmitri Donskoï to appear before him, and received a curt refusal. Tamerlane sent one of his generals with an immense army to Moscow, and Dmitri, not finding the former support, went to Kostroma to collect troops. The Tartars appeared before Moscow, which they tried to carry by assault but failed. They pretended to enter into negotiations, when they surprised the gates and Moscow was delivered up to fire and sword. It is said that 24,000 inhabitants were slaughtered. Vladimir and other towns suffered the same fate.
It is told that Dmitri wept when he saw the charred remains of his capital after the Tartars had withdrawn. There was nothing for it but to make peace with the khan, and once more the Tartar tax gatherers went their rounds. But Dmitri's heart was sore against the Dukes of Tver and Riazan who had abetted Mamaï, and Novgorod, which had used the opportunity of Moscow's distress to plunder some of its towns. After the country had sufficiently recovered, he compelled the Duke of Riazan to conclude "a perpetual peace," and Novgorod paid an indemnity besides agreeing to an annual tribute.
When Dmitri died in 1389, he left Moscow the most powerful of Russian dukedoms. He was succeeded by his eldest son Vassili, with the consent of his cousin Vladimir, who was the eldest of the family. Vassili mentioned Novgorod as "his patrimony," and acted as if the republic was his private property. He visited Saraï in 1392, and while there bought an iarlikh, which placed him in possession of Souzdal, Nishni Novgorod, and Mourom. In 1393, the people of Novgorod revolted, but Vassili's army convinced them that the republic was fast losing its former power.
At this time Tamerlane, dissatisfied with his generals, arrived in Europe and after pillaging the Golden Horde, moved westward, spreading ruin and desolation. He drew near to Moscow, where the famous eikon of the Virgin was taken in solemn procession, when the Tartar army stopped and turned to the south, where Azof, Astrakhan, and Saraï, were plundered and destroyed. (1395.) After Tamerlane's withdrawal, Vassili pretended not to know to whom to pay the tribute,—and so paid none at all. The Tartars under Ediger marched upon Moscow to collect it, but the city was bravely defended and Ediger, fearing an invasion from Asia, agreed to accept a ransom of 3000 rubles, which was paid by the boyards.
More dangerous were the attacks of Vitovt of Lithuania, Vassili's father-in-law, who marched three times against Moscow. Both Vitovt and Vassili were indisposed to risk a decisive battle, fearing that, if defeated, their enemies would despoil them. In 1408 a treaty was signed whereby the Ouger was made the frontier between them. This gave Smolensk to Lithuania, and Kozelsk to Moscow.
Vassili extended his territory, and with it his name; one of his daughters married the Byzantine Emperor, John Palaeologus. At his death, in 1425, he left his territory to his son Vassili, the Blind, whose title was contested by his uncle George, on the ground of being the eldest of the family. The dispute was submitted to the khan, in 1431. Both sides humbled themselves, but the argument of Vassili's boyards prevailed. "My Lord Czar," they said to the khan, "let us speak,—us, the slaves of the grand duke. Our master, the grand duke, prays for the throne of the grand dukedom, which is your property, having no other title but your protection, your investiture, and your iarlikh. You are master and can dispose of it according to your good pleasure. My Lord, the Duke George, his uncle, claims the grand dukedom by the act and will of his father, but not as a favor from the all-powerful." Vassili the Blind, was the first grand duke to be crowned at Moscow instead of at Vladimir.
His reign was disturbed by constant wars with his uncle, and afterwards with his cousins. In 1446 he was taken prisoner by one of the latter, who ordered his eyes to be put out. In 1450, peace was restored when the second son of George died of poison. Notwithstanding the loss of his sight Vassili displayed considerable energy in reëstablishing his authority. Novgorod was forced to pay another indemnity, and to give a written promise that in future all deeds would be void unless stamped with the seal of the grand duke.
The most remarkable incident of Vassili's reign was the Council at Florence, Italy, in 1449, where delegates of the Roman and Greek Churches tried to effect a union. There were seventeen Metropolitans, among them Isidore of Moscow, who signed the Act of Union. When Isodore returned and declared what he had done, a great opposition appeared. Vassili himself insulted the Metropolitan, who fled to Rome. In 1453, Mahomet II captured Constantinople when a host of priests, monks, artists, and learned men fled from the extinct Byzantine Empire, to find an asylum in Russia.