Treaty of Hadiach
After the Treaty of Pereyaslav in 1654, Ukraine became a suzerainty under the protection of the tsar of Russia, although for a considerable period of time it enjoyed nearly complete autonomy. After the death of Bohdan Khmelnytsky in 1657, his successor Ivan Vyhovsky initiated a turn towards Poland, alarmed by the growing Russian interference in the affairs of the Hetmanate. An attempt was made to return to the three-constituent Commonwealth of nations with the Zaporozhian cossacks joining the Polish–Lithuanian Commonwealth by signing the Treaty of Hadiach (1658). The treaty was ratified by the Sejm but was rejected at the Hermanivka Rada by the Cossack rank and file, who would not accept a union with Catholic Poland, which they perceived as an oppressor of Orthodox Christianity. The angered cossacks executed "Polkovniks" Prokip Vereshchaka and Stepan Sulyma, Vyhovsky's associates at the Sejm, and Vyhovsky himself narrowly escaped death.