The eastward expansion of Dutch colonists ushered in a series of wars with the southwesterly migrating Xhosa tribe, known as the Xhosa Wars, as both sides competed for the pastureland near the Great Fish River, which the colonists desired for grazing cattle. ''Vrijburgers'' who became independent farmers on the frontier were known as ''Boers'', with some adopting semi-nomadic lifestyles being denoted as . The Boers formed loose militias, which they termed ''commandos'', and forged alliances with Khoisan peoples to repel Xhosa raids. Both sides launched bloody but inconclusive offensives, and sporadic violence, often accompanied by livestock theft, remained common for several decades.