Colombia's central government has never been able to control all of its territory. The Magdalena River Valley represents the heart of the country, where — along with the cities of Bogota, Medellin and Cali — most of the country's population lives. It is isolated from the rest of the country by Andes mountain ranges on either side. Outside the heartland is a combination of jungles, mountains and plains, largely uninhabited with limited infrastructure development. Even with U.S. military aid, the logistical challenges involved in projecting power into Colombia's hinterlands make extended deployments unsustainable. Military operations outside the core have never been able to establish the security conditions needed to permit effective law enforcement on a large scale or for a significant period of time. The Colombian state is thus largely absent from the hinterlands, and the economic inequality in these regions is severe, giving rise to criminal organizations and insurgent groups like the Revolutionary Armed Forces of Colombia (FARC). This would not be a point of contention if not for the fact that the regions outside Colombia's core are rich in extractive resources such as oil, gold, precious stones, and rare earth elements — as well as marijuana, coca and opium poppies. The state and insurgent and criminal groups are in competition for these resources. Because the government lacks the resources to properly address the underlying issues of lack of development and inequality, eliminating insurgent groups is almost impossible. Instead, the government must concentrate on inhibiting their ability to operate and attempt to secure its interests as it seeks ways to improve conditions in the countryside.