SUMMARY

Frente Oliver Sinisterra (FOS) was a former FARC front named after Óscar Armando Sinisterra Sevillano, alias Oliver, who was the leader of the FARC in Nariño until his death in 2015.

Frente Oliver Sinisterra was fighting the Government of Colombia, other guerilla groups, such as ELN, and paramilitary groups, such as Autodefensas Gaitanistas de Colombia, over territorial control for drug trafficking in western Nariño. More specifically, the activities were centered around Tumaco in Colombia and areas bordering the Ecuadorean province of Esmeraldas.

Walter Arizala Vernaza, alias Gaucho, created FOS after abandoning a demobilization process of former FARC fighters, following the signed peace agreement in 2016. Gaucho died in 2018 in a joint military and police operation launched by Colombia and Ecuador near Tumaco in Nariño. Following the death of El Gaucho, Carlos Arturo Landazuri, El Comandante Gringo a.k.a. ‘Fabian’, another founding member of FOS assumed leadership of the group.

Frente Oliver Sinisterra was known for its use of unconventional weapons, such as anti-personnel mines, fuel bombs triggered by passing army troops and explosives targeting army helicopters. Allegedly, drones were also used to transport explosives to remote parts of Colombia.

The group started out with about 250 members and is believed to have had between 300-500 members in its peak years 2018-2019. Towards the end of 2019, FOS was weakened due to disputes with the United Guerrillas of the Pacific (GUP) and Los Contadores in fighting over coca cultivation enclaves.

In its most active years, Frente Oliver Sinisterra became the main cocaine supplier to the Sinaloa Cartel.

Frente Oliver Sinisterra has been involved in the one-state category of UCDP organized violence.