Vasily II is the youngest son of Vasily I of Moscow by Sophia of Lithuania, the only daughter of Vytautas the Great, and the only son to survive his father (his elder brother Ivan had died in 1417 at the age of twenty-two).

On his father's death at fifty-four in 1425, ten-year-old Vasily is proclaimed Grand Duke.

His mother acts as a regent.

His uncle, Yuri of Zvenigorod (Prince of Galich-Mersky), and his two sons, Vasily the Cross-Eyed and Dmitry Shemyaka, seize on the opportunity to advance their own claims to the throne.

These claims are based on the Testament of Dmitri Donskoi, Yuri's father and Vasily's grandfather, who had stated that if Vasily I died Yuri would succeed his appanage.

However, Dmitri had written the testament when Vasily I had no children of his own, and it might be argued that this provision had been made only for the case of Vasily's childless death.

Vasily's claim is supported by Vytautas, his maternal grandfather, and by the boyars.