At the end of the 15th century, the groups of warriors who called themselves Cossacks appeared on the territory between the borders of Lithuania, Muscovy and the Crimea, in the "wild steppes" of Zaporizhia. From the 16th century the Sich became their military centre. Zaporizhian Cossacks participated in the wars on the side of the Commonwealth: the Livonian War (1558-1583), the Polish-Muscovite War (1605-1618), Khotyn war (1620-1621), and Smolensk war (1632-1634). Cossacks also organized their own campaigns in Moldavia, Muscovy, and Crimea, on the Black Sea coast of Bulgaria and in Asia Minor for looting. They willingly became mercenaries, particularly during the Thirty Years' War (1618-1648).