The AUC (Autodefensas Unidas de Colombia or United Self-Defense Forces/Group of Colombia), is commonly referred to as "the paramilitaries."  It is an umbrella organization formed in 1997 to coordinate the activities of local paramilitary groups and develop a cohesive paramilitary effort to combat Marxist guerrillas.

The 20,000-strong paramilitary forces are notorious for two things: massacres of civilians they consider sympathetic to the guerrillas and their close links with the cocaine trade. Historically, paramilitaries have also enjoyed the collaboration, support and toleration of units of the Colombian security forces, a fact that has led many to refer to the paramilitaries as a "sixth division" of the army.

The AUC is based in northern Colombia, where the drug traffickers and landowners who support the group hold sway. During the 1990s, AUC extended its reach and now operates throughout central and western Colombia.

In 2003, paramilitary commanders initiated demobilization negotiations with the Uribe administration, in the hope of obtaining a deal that would allow them to avoid extradition and potentially lengthy prison terms in the U.S. for drug trafficking.

On November 25, 2003, television viewers in Colombia watched as over 860 paramilitaries belonging to Medellin's Bloque Cacique Nutibara, which took control of La Sierra from Bloque Metro, laid down their arms in a staged ceremony in front of Colombian and foreign dignitaries. The ceremony marked the first of a series of large-scale demobilizations of AUC-linked paramilitary groups around the country. On March 10, 2006, less than two days before Colombia's legislative elections, the AUC completed the demobilization process, with approximately 28,000 right-wing fighters accepting the government's offer of reduced jail terms for such crimes as massacre, torture and cocaine smuggling in exchange for laying down arms.

However, paramilitary infiltration of Colombian politics continues to be an issue. Many Colombians fear that the paramilitaries will continue to use intimidation and bribery to influence the political landscape. Also, the Organization of American States, which supervised the demobilization process, denounced several paramilitary groups for beginning to rearm in northeastern Colombia.

(from PBS.org series on Colombia http://www.pbs.org/independentlens/lasierra/rebels.html)