 Complete the following phrase:  The Cossack Khmelnytsky Uprising of 16481657 engulfed the south-eastern regions of the Polish crown; its long-term effects were disastrous for the Commonwealth. The first liberum veto a parliamentary device that allowed any member of the Sejm to dissolve a current session immediately was exercised by a deputy in 1652. This practice would eventually weaken Polands central government critically. In the Treaty of Pereyaslav 1654, the Ukrainian rebels declared themselves subjects of the Tsar of Russia. The Second Northern War raged through the core Polish lands in 16551660; it included a brutal and devastating invasion of Poland referred to as the Swedish Deluge. The war ended in 1660 with the Treaty of Oliva, which resulted in the loss of some of Polands northern possessions. In 1657 the Treaty of Bromberg established the independence of the Duchy of Prussia. The Commonwealth forces did well in the 