Земский собор
Although the Zemsky Sobor of 1651 was poised to accept the Cossacks into the Moscow sphere of influence and to enter the war against Poland–Lithuania, the Tsar waited until 1653, when a new popular assembly eventually authorized the protectorate of Ukraine with Tsardom of Russia. After the Cossacks ratified the agreement at the Pereyaslav Council, the Russo-Polish War became inevitable.