raids into neighboring countries. The registered Cossacks were paid from 5 to 12 zlotys each quarter, and the Zaporizhian Sich was selected as their headquarters. As the Polish interests aimed in securing the Swedish crown, however, the Cossack movement was allowed to grow out of control, leading to a series of local rebellions by polkovnyk Krzysztof Kosiński and Severyn Nalyvaiko, with assistance from kosh otaman of the Zaporozhian Cossacks Hryhoriy Loboda. Organization Registered Cossacks formed an elite among the Cossacks, serving in the military under officers (starshyna), colonels (polkovnyk) and generals (hetman), under the Grand Crown Hetman (the highest Commonwealth military commander). A substantial minority of Cossacks formed skilled light cavalry units (choragiew), excellent skirmishers trained in mounted archery (and later using firearms), making lightning raids, harassing heavier, slower formations and disengaging. Those units were often used as support for heavy elite Commonwealth cavalry, the husaria, and were much cheaper to form than a hussar unit. The main Cossack units were the infantry, known for their tabor formation. Registered Cossacks had many privileges, including personal freedom, exemption from many taxes and duties, and the right to receive wages, although the Commonwealth military's fiscal problems, led to delayed payments, often via items like clothing or weapons instead of coin. Many Cossacks were skilled warriors and their major income source came from raids on the southern neighbors of the Commonwealth: the (Ottoman Empire and its vassals). However, only a small number were actually 'registered Cossacks'; the exact number was from few hundred to few thousand and varied over time, usually increasing during wartime. This led to many social and political tensions, especially as szlachta (Polish and Ukrainian gentry) continually attempted to force the Cossacks into submission as peasants, while the Cossacks demanded significant expansions of the Cossack register. Furthermore, the Cossack-szlachta conflict was aggravated as Cossacks often supported Commonwealth monarchs like Wladyslaw IV Waza who were at odds with Polish szlachta who wished to further limit the monarch's powers. The tensions between the Cossacks and szlachta grew from the late 16th century and resulted in several uprisings with the registered Cossacks often forced to choose sides between supporting their own people or the szlachta-backed Commonwealth forces. Eventually the king's refusal to expand the registry led to the Khmelnytsky uprising of 1648. A Russian-Polish alliance was formed against Bohdan Khmelnitsky, with his Cossacks being declared rebels against all order. Don Cossack raids on