Treaty of Hadiach
In 1656, Russia signed a peace accord in Vilno with Poland in violation of the Treaty of Pereyaslav of 1654, and increased pressure on the Cossack Hetmanate. As a result, Vyhovsky entered into negotiations with the Poles, and concluded the Treaty of Hadiach on 16 September 1658. Under the planned new treaty three voyevodships of central Ukraine (Kiev, Bratslav and Podilya) were to become an equal constituent nation of the Polish–Lithuanian Commonwealth along with Poland and Lithuania under the name of Grand Principality of Rus', forming the Polish–Lithuanian–Ruthenian Commonwealth. However, the Sejm ratified the treaty in a very limited version, where the idea of an independent Ruthenian Principality was completely abandoned.