Registered Cossacks
One of the leaders of the "Blacks", or poor peasants and non-registered Cossacks, Pavel Mikhnovych But nicknamed Pavlyuk, gathered around himself a large band of armed Zaporozhian Cossacks and reached the fortress town of Korsuń, the headquarters of the Registered Cossacks and the largest Polish royal outpost in the Borderlands. Pavlyuk had already taken part in the earlier Sulima Uprising of 1635, but was pardoned when he promised not to rise arms against the Commonwealth again.