sentences:  Traditionally the zone was controlled by the leftist Ejército de Liberación Nacional.During the 1995-1998 time period, it was subject to intense combat and a scenario of continuing murder perpetrated by paramilitary groups, which succeeded in gaining control of the area.The presence of the paramilitary group Autodefensas Campesinas de Casanare, whose base of operations was in the nearby municipalities of Villanueva and Monterrey, was a constant until 2004 when the group surrendered the zone to the Autodefensas Unidas de Colombia AUC, in a battle which is said to have cost more than 3.000 lives.