The foco theory of revolution by way of guerrilla warfare, also known as focalism (Spanish: foquismo [foˈkizmo]), was formulated by French intellectual and government official Régis Debray, whose main source of inspiration was Marxist revolutionary Ernesto "Che" Guevara's experiences surrounding his rebel army's victory in the 1959 Cuban Revolution.
Its central principle is that vanguardism by cadres of small, fast-moving paramilitary groups can provide a focus (in Spanish, foco) for popular discontent against a sitting regime, and thereby lead a general insurrection. Although the original approach was to mobilize and launch attacks from rural areas, many foco ideas were adapted into urban guerrilla warfare movements by the late 1960s.
Like other leaders of his time, such as Mao Zedong, Ho Chi Minh and Amílcar Cabral, Che Guevara believed that people living in countries still ruled by colonial powers, or living in countries chained by what he saw as a new form of economic exploitation, could best defeat what he perceived as colonial powers by taking up arms. Like other theoreticians, Guevara also believed that armed resistance needed to be built not by concentrating one's forces in urban centers, but rather through accumulation of strength in mountainous and rural regions where the enemy's presence was weakest.
Cuban Revolution 
Foquismo, which was formally theorized by Régis Debray, draws on Ernesto Guevara's experience of the 1959 Cuban Revolution, where a small group of 82 members landed in Cuba on board of the Granma, in December 1956, and initiated a guerrilla war in the Sierra Maestra. During two years, the poorly armed escopeteros, at times fewer than 200 men, managed to win victories against Batista's army and police force, which numbered between 30,000 and 40,000 in strength. The small group finally managed to take Havana after the December 1958 Battle of Santa Clara.
This surprising success led to the foquismo theory which, inspired by Mao's doctrine of people's war, counted on the support of the people to win the war. But the foquismo theory stated that this popular support would be created during the armed struggle itself: thus, against predominant Marxist theory, there was no need to wait for the "objective conditions" of a popular uprising to engage the last stage of the revolutionary struggle (i.e. armed struggle). In other words, a small group of revolutionaries was considered to be enough to jumpstart a revolution since this group could begin the revolutionary struggle while at the same time developing the conditions necessary for popular support for the revolution. This theory focused heavily on the notion of vanguardism and on the moral value of the example.
While focalism drew from previous Marxist-Leninist ideas, including a unique, adaptive blending of Stalinist tactics and the Maoist strategy of "protracted people's war", it also broke with many of the mid-Cold War era's established communist parties. Despite Nikita Khrushchev's eager support for "wars of national liberation" and the focalists' own enthusiasm for Soviet patronage, Cuba's own Partido Socialista Popular had retreated from active confrontation with the Fulgencio Batista regime, so Castroism/Guevarism substituted the foquista militia for the more traditional vanguard party.
In La Guerra de guerrillas (Guerrilla Warfare), Guevara did not count on a Leninist insurrection led by the proletariat as had happened during the 1917 October Revolution, but on popular uprisings which would gain strength in rural areas and would overthrow the regime: the vanguard guerrilla was supposed to bolster the population's morale, not to take control of the state apparatus itself and this overthrow would occur without any external or foreign help. According to him, guerrillas were to be supported by conventional armed forces:
"It is well established that guerrilla warfare constitutes one of the phases of war; this phase can not, on its own, lead to victory."
In power, Castro sided with the USSR in the 1961 Sino-Soviet split, while Guevara sympathized with the People's Republic of China. Perhaps accelerated by this divide, the latter man shifted his energies away from Cuba to adventurism, promoting guerrilla focos overseas. Though this method had triumphed in Cuba, Guevara saw it subsequently fail in Africa and Latin America. Laurent-Désiré Kabila put it in practice in Congo. Despite being backed by the Castro regime, Guevara's attempt to forge an insurgency in Bolivia led to his capture and subsequent execution in 1967.
Foco after Guevara 
Guevara's unsuccessful campaign in Bolivia dampened Cuba's overt support of focoist uprisings internationally for several years, and many revolutionary movements split into different factions, particularly New Left, Maoist and/or urban guerrilla breakaways from previous Moscow-line parties and/or foco groups. By the mid-1970s, however, Cuba revived and further escalated its previous zeal, directly deploying its military in Africa before the collapse of détente—e.g., supporting up the MPLA government in Angola.
In Argentina, the People's Revolutionary Army (ERP), led by Roberto Santucho, attempted to create a foco in the Tucumán Province. The attempt failed after the government of Isabel Perón signed in February 1975 the secret presidential decree 261, which ordered the army to neutralize and/or annihilate the ERP insurgency (which was not supported by a foreign power, and also lacked popular support). Operativo Independencia gave power to the Argentine Armed Forces to "execute all military operations necessary for the effects of neutralizing or annihilating the action of subversive elements acting in the Province of Tucumán."
General Acdel Vilas immediately deployed over 3,000 soldiers, including conscripts from the Fifth Infantry Brigade and two companies of elite commandos. While fighting the guerrillas in the jungle, Vilas concentrated on uprooting the ERP support network in the towns, using state terror tactics, inspired by the 1961 Battle of Algiers, later adopted nation-wide, as well as a civic action campaign. The ERP was quickly defeated, but this military campaign marked the beginning of the Dirty War in Argentina.
Central America 
After victories for a once-divided, recently-reunited Sandinista movement in Nicaragua and the United Front-style New Jewel Movement in Grenada in 1979, Castro effectively supported the creation of the FMLN of El Salvador by pushing for the merge of five other communist factions between December, 1979 and October, 1980. Similarly, Cuba supported four rival guerrilla groups' decision to form the URNG coalition of Guatemala in 1982.
See also 
- The Legacy of Che Guevara: Internationalism Today by Dr. Peter Custers, Sri Lanka Guardian, February 24, 2010
- Bockman, chapter 2.
- Ernesto Che Guevara (French ed.: Oeuvres I, Petite collection Maspero, 34, 1968, p.32
- Guevara, Che. "Guerrilla War: A Method."
- Decree No. 261/75. NuncaMas.org, Decretos de aniquilamiento.