In 1609 the Zebrzydowski Rebellion ended when Tsar Vasili signed a military alliance with Charles IX of Sweden (on 28 February 1609). The Commonwealth king Sigismund III, whose primary goal was to regain the Swedish throne, got permission from the Polish Sejm (Parliament) to declare war on Russia. He viewed it as an excellent opportunity to expand the Commonwealth's territory and sphere of influence, with hopes that the eventual outcome of the war would Catholicize Orthodox Russia (in this he was strongly supported by the Pope) and enable him to defeat Sweden. This plan also allowed him to give a purpose to the numerous restless former supporters of Zebrzydowski, luring them with promises of wealth and fame awaiting members of the campaign beyond the Commonwealth's eastern border. A book published that year by the well-travelled Polish Silesian nobleman, courtier and political activist Paweł Palczowski of Palczowic, "Kolęda moskiewska" ("The Muscovite Carol"), compared Russia to the Indian empires of the New World, full of golden cities and easy to conquer. The treatise was written to promote Polish colonialism and persuade delegates of the Sejm in January 1609 to support Sigismund III's expedition to Muscovy. Palczowski himself participated in and perished during Sigismund's Muscovy expedition. Some Russian boyars assured Sigismund of their support by offering the throne to his son, Prince Władysław. Previously, Sigismund had been unwilling to commit the majority of Polish forces or his time to the internal conflict in Russia, but in 1609 those factors made him re-evaluate and drastically change his policy.