Feb 1 (Reuters) - Colombia's FARC guerrillas freed four members of the security forces on Sunday, their first release of kidnap victims in more than a year.

Here are some facts about the Revolutionary Armed Forces of Colombia (FARC), Colombia's largest rebel group and Latin America's oldest left-wing insurgency:

* The FARC was established in the 1960s as a Marxist peasant army fighting for land reform and to reduce the gulf between rich and poor in the South American country.

* Branded terrorists by the United States and the European Union, the FARC has been driven onto the defensive by President Alvaro Uribe's U.S.-backed military crackdown. Washington has given Colombia $5.5 billion in mostly military aid since 2000.

* U.S. and Colombian authorities say the FARC uses the multibillion-dollar Colombian cocaine trade and extortion to fund its operations. Colombia's four-decade-old conflict is now often a fight over drug-producing land involving the FARC, illegal paramilitaries and narcotics trafficking gangs.

* Violence has eased and the economy has expanded in most of Colombia's cities, but the FARC remains a powerful force in the southern jungle regions where the state's presence is weak.

* Better military mobility, improved state intelligence and government rewards for informants have hit the FARC's ability to move and communicate. The guerrilla group has also been weakened by desertions.

* In July last year, military commandos posing as aid workers rescued French-Colombian politician Ingrid Betancourt, a former presidential candidate, and three Americans, high-profile hostages who had all been held for years in jungle camps.

* The FARC said its founder Manuel Marulanda died last March of natural causes after four decades fighting the state. He was a cohesive figure among the guerrilla force's military and political wings.

* During the same month, Raul Reyes, a FARC spokesman and contact for negotiations over hostages, was killed in his camp hidden in Ecuador in a cross-border strike that sparked a diplomatic crisis in the Andean region. Another commander, Ivan Rios, was killed in March by a bodyguard who chopped off the leader's hand as proof in order to claim a government reward.

* In October, a FARC commander deserted, taking with him a politician held hostage for more than eight years. The government said the escape showed how the rebels are falling apart and offered the guerrilla deserter asylum in France. (Writing by Patrick Markey, editing by Anthony Boadle)

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