The nearly continuous wars of the first three decades of the new century resulted in modernization, if not (because of the treasury limitations) enlargement, of the Commonwealth's army. The total military forces available ranged from a few thousands at the Battle of Kircholm, to the over fifty thousands plus pospolite ruszenie mobilized for the Khotyn (Chocim) campaign of 1621. The remarkable during the first half of the 17th century development of artillery resulted in the 1650 publication in Amsterdam of the "Artis Magnae Artilleriae pars prima" book by Kazimierz Siemienowicz, a pioneer also in the science of rocketry. Despite the superior quality of the Commonwealth's heavy (hussar) and light (Cossack) cavalry, the increasing proportions of the infantry (peasant, mercenary and Cossack formations) and of the contingent of foreign troops resulted in an army, in which these respective components were heavily represented. During the reigns of the first two Vasas a war fleet was developed and fought successful naval battles (1609 against Sweden). As usual, fiscal difficulties impaired the effectiveness of the military, and the treasury's ability to pay the soldiers.