sentences:  Boris Godunov then convened a "Zemsky Sobor", a national assembly of boyars, church officials, and commoners, which proclaimed him tsar, although various boyar factions refused to recognize the decision.Widespread crop failures caused the Russian famine of 1601–1603, and during the ensuing discontent, a man emerged who claimed to be Tsarevich Demetrius, Ivan IV's son who had died in 1591.This pretender to the throne, who came to be known as False Dmitriy I, gained support in Poland and marched to Moscow, gathering followers among the boyars and other elements as he went.