At the time of the 1537 Spanish invasion, the Páez were organized in a series of warring chiefdoms coexisting in Tierradentro with other ethnic communities, including the Guambiano, the Pijao, and the Yalcón, and linked with them through relations of warfare, trade, and marriage. During the first century of the Conquest, the aboriginal population of approximately 10,000 was halved through war and disease. The Spanish forced the Indians into centralized villages so that they would be more easily exploitable as a source of labor and tribute. Communities began to migrate to the western slopes of the cordillera, founding new towns. In the early eighteenth century native leaders validated their political authority and the territories under their dominion through the creation of reservations, or resguardos, legitimized through titles granted by the Spanish Crown. During the nineteenth century the communal landholdings of the resguardo were challenged by non-Indian landowners, by gatherers of quinine bark, by the ravages of civil war, and by national legislation that sought to privatize landownership throughout the country. At the turn of the century the Páez joined a political movement led by sharecropper Manuel Quintín Lame, who fought to reclaim lost lands and to free Indian sharecroppers from paying rent for the plots they tilled. Non-Páez sharecroppers evicted from their lands in neighboring regions colonized Tierradentro in the 1930s, arousing heightened militancy among the land-poor Páez. During the 1950s, Tierradentro was beset by violence and civil war, and some communities were forced to disperse.