The grand knyaz Ivan III signed a treaty with the knyaz Mikhail Andreyevich Vereysky. According to the treaty, knyaz Mikhail bequeathed the principality of Beloozero to the grand knyaz. This will violated the rights of Mikhail's son, Vasily, and signified the new phase in Russian history: the annexation of the appanage duchies.
In 1382 the knyazes of Beloozero and Vereya, Fyodor Romanovich and his son Ivan, were killed in the battle of Kulikovo field and the grand knyaz of Moscow Dimitri Donskoy, the victor in this battle, became the knyaz of these districts. In 1389, Dimitri Donskoy devised the districts of Vereya and Beloozero to his third son, Andrey. Andrey was very young and the real ruler of Beloozero was a knyaz from the old dynasty, a relative of Fyodor Romanovich and Ivan. Soon Andrey grew up and acceded to the throne.
The heirs of Andrey Dimitriyevich, Ivan and Mikhail, split the principality into two parts. Ivan got Mozhaisk and Mikhail got Beloozero and Vereya. When Vasily II of Moscow (died in 1462) waged wars against the knyazes of Galich and Zvenigorod, Mikhail always supported Muscovy, while Ivan attempted to retain the autonomy and often opposed Vasily. In the end, Ivan had to flee to Lithuania and Mikhail remained the only ruler of the principality. Nevertheless, Vasily gradually limited his rights till, in 1482, Mikhail had to bequeathe the principality to Vasily. In 1483, Ivan III forced Mikhail's son, Vasily the Bold, to follow his uncle and to escape to Lithuania. On 9 April 1486 Mikhail died and Vereya, Beloozero and Mozhaisk got the new knyaz — Ivan III. After 1482 Ivan III signed similar treaties with many other principalities, including Ryazan and Tver. Vyatka and Novgorod were forced to obedience. Kazan was seized and the whole khanate of Kazan was annexed. Vyazma was taken from Lithuania after a 1.5-year long war. In 1483 Ivan Travin and knyaz Fyodor Kurbsky crossed the Urals and travelled till the estuary of river Ob, while the leaders of the native population pledged allegiance to Muscovy and became vassals of Ivan III. One could say that this was the time when Russia as we know it today appeared from a loosely coupled agglomerate of principalities and neighboring countries.