 Under increasing pressure from the Polish–Lithuanian Commonwealth, in the mid-17th century the Sich declared an independent Cossack Hetmanate.The Hetmanate was initiated by a rebellion under Bohdan Khmelnytsky against Polish and Catholic domination, known as the Khmelnytsky Uprising.Afterwards, the Treaty of Pereyaslav (1654) brought most of the Cossack state under Russian rule.