When 39 years old Dimitri died, his elder son, Vasily, inherited the title of the grand knyaz of Vladimir and a part of the Moscow appanage. The other parts of Muscovy were split between the other sons. Dimitri's will was written in slightly vague terms and his second son Yuri interpreted them in the way that he was to succeed Vasily. This was not the case, but Yuri continued to insist on his interpretation.
During the rule of Vasily Dimitrievich (1389-1425) Mongols attacked Rus twice. Leveraging the support of khan Tokhtamysh, Vasily occupied Nizhny Novgorod, controlled by the knyazes of Suzdal. Tokhtamysh was dethroned by Tamerlane and the relations between Rus and the Mongols deteriorated. Vasily expected a large scale military campaign and gathered a large army. Metropolitan Cyprian proposed to bring to Moscow the icon of St. Mary, brought from Kiev by Andrei Bogolyubski to Vladimir (see chapter 31). Tamerlane, however, turned back from Yelets. The second attack of Mongols was organized by Edigu khan, angered by Vasily's reluctance to pay tribute. Edigu secretly entered Rus and besieged Moscow in 1408. Vasily left Moscow and went to the north, and Edigu sacked his lands and returned to the Horde. Vasily continued his father's inimical policy to Lithuania. Strengthening Lithuanian knyazes subjugated Russian lands in upper Dnieper and Western Dvina. This was also the goal of Muscovy. Vasily was married on Sophia, the daughter of Vytautas, but in spite of this kinship, they even led open wars with each other. Finally, Rus and Lithuania agreed to recognize river Ugra the border of the two countries. After the peace was signed, Vasily made Vytautas the tutor of his son (and Vytautas' grandson) Vasily Vasilievich.
Vasily Vasilievich, later named the Dark (that is blind) was ten years old when his father died. He ruled since 1425 till 1462 and this was a hard time. His uncle Yuri, knyaz of Galich on river Kostroma (not the Galich in south-western Rus), refused to recognize Vasily the grand knyaz. When Vytautas died, Yuri layed his claims to the throne of Rus. Yuri and his sons Vasily Kosoy (the Squit-Eyed) and Dimitri Shemyaka began struggle against Vasily. This feud went on for about twenty years (1430-1450) and was a cruel one. So, Vasily ordered to blind captured Vasily Kosoy, and was blinded later himself by Dimitri Shemyaka. Moscow often changed hands till Vasily got it and the lands of his enemies. During this conflict the new order of succession based on father-to-son inheritance was finally established. The majority of the population, clergy and boyars supported Vasily and this new order of succession, which promised more stability and led to autocracy.
During this feud the Mongols continued raiding Rus. One of the results of the dissolution of the Golden Horde was that many Mongol murzas (dukes, or knyazes) were evicted from the Horde and had to search for protection. Some of them were hired by the Muscovy knyazes, while other began to rob their lands and were attacked by Russians. One of the best known among them was Ulu-Makhmet. After he had sacked Russian provinces on Oka, he went to Volga and built a town for himself called Kazan. Having established the Kazan khanate, he began raiding Rus and even attacking Moscow. Vasily Vasilievich attempted to oppose him, but was defeated and captured in 1445 near Suzdal. Muscovites panicked and expected a major raid, but the Mongols received a huge ransom and released Vasily. The money were, of course, collected from Russian people. Their discontent grew when Vasily brought a large number of Mongols with him, who became his servants. It was then that Shemyaka captured Vasily and blinded him.
An important event in the history of the Russian church took place in these years. In 1439, in Florence, on the congress of orthodox and catholic clergy the union of the western and eastern christian churches was signed. The emperor and the patriarch of Constantinople sought for this union, hoping that the pope and the western countries would help them opposing the Turks. They were ready to any concessions, and the terms of the union were clearly disadvantageous for the Greeks. They retained their rituals, but had to accept the catholic dogmata and the leadership of the popes. At the same time when Constantinople was preparing for the congress, the metropolitan of Rus had to be appointed. Isidore, a learned man who was inclined towards the union, was appointed. As soon as he arrived to Moscow, he began to get ready for the travel to Italy. He became one of the most vigorous proponents of the union in Florence. In 1441 he returned to Moscow and proclaimed the union with the catholic church. For centuries Greeks raised animosity towards catholicism in Russians, and this union was not accepted. Isidore was taken in custody, but he managed to escape to Lithuania and from there he departed to Italy. And the Muscovy decided to secede from the Constantinople patriarchate, which in their eyes had betrayed the orthodoxy, and to elect the metropolitan on the congress of Russian hierarchs. The bishop of Ryazan Jonas was elected the first independent metropolitan of Rus. The south-western Rus, the former Kievan metropoly, however, still received their metropolitans from Constantinople.