Julio César Méndez Montenegro

It was during the Mendez presidency that the United States dramatically expanded its military mission in Guatemala. Within days of Mendez taking office, US Colonel John Webber Jr. was dispatched to the country to assist in modernizing Guatemala's counterinsurgency apparatus. Under Colonel Webber's command, the United States expanded training within Guatemala's 5,000-man army and outfitted the Guatemalan security forces with the most modern counterinsurgency equipment available. The United States also assisted the Guatemalan security forces in the implementation and use of counter-terrorism, and the establishment of counter-terror units under the supervision of U.S. police advisors. With increased US military support, the Guatemalan Army launched a counter-insurgency campaign that successfully combated and dispersed the left-wing guerrilla organizations fighting in the mountains and country. The guerrillas, including the Rebel Armed Forces (Fuerzas Armadas Rebeldes — FAR), then concentrated their attacks in Guatemala City, assassinating many leading representatives of the military government, U.S. military advisors, and the American ambassador John Gordon Mein, in 1968.

The government's use of "any means necessary" resulted in the opposition increasing its level of resistance to ensure its survival. The "White Terror" (which led to the destruction of the FAR's ladino peasant base in the eastern provinces) caused the MR-13 to retreat to Guatemala City. There, the MR-13 began to engage in selective killings of members of the security forces as well as U.S. military advisors. The insurgents assassinated the American ambassador to Guatemala, John Gordon Mein, in 1968, and the German ambassador to Guatemala, Karl Von Spreti, in 1970.

Following the inauguration of Méndez Montenegro, he appointed Colonel Rafael Arriaga Bosque to Defense Minister. Mendez activated the 'Special Commando Unit of the Guatemalan Army' (SCUGA). The SCUGA was placed under the command of Colonel Máximo Zepeda in January 1967, after which point it assumed command over most of the Guatemalan government's urban counterinsurgency operations against PGT. Composed of both military and civilian personnel, the SCUGA functioned both as a counter-terror apparatus and as an intelligence-gathering apparatus. SCUGA commandos routinely carried out abductions, bombings, street assassinations, torture, "disappearances" and executions of both documented and suspected communists. The SCUGA often collaborated with the Fourth Corps of the Guatemalan National Police, which carried out similar activities. Together these forces often carried out various counter-terror and counter-insurgency operations under the guise of fictitious paramilitary death squads and anti-communist front organizations (known by acronyms such as the NOA, CADEG, CRAG and RAYO). In addition to engaging in operations under the guise of para-militarism, the SCUGA nominally worked with paramilitary death squads such as the infamous Mano Blanca ("White Hand").

In 1966, the left-of-center Méndez defied odds after being elected and successfully sworn in as President of Guatemala. As a civilian who previously made a career as a law professor, Méndez's election, despite challenges, was also considered a historical transition from longstanding military rule in Guatemala. At the time of Méndez's election, Juan Jose Arévalo, who served as President of Guatemala from 1945 to 1951, was the only civilian to complete a full presidential term since Guatemala's independence in 1847.

In March 1966, thirty Guatemalan Party of Labour (PGT) associates were kidnapped, tortured, and killed by the security forces. This was one of the first major instances of forced disappearance in Latin American history. These 30 disappearances marked the beginning of a dramatic increase of state repression in 1966. When law students at the University of San Carlos used legal measures (such as habeas corpus petitions) to require the government to present the detainees at court, some of the students were "disappeared" in turn.

Mano Blanca, or the Movement of Organized Nationalist Action, was set up in 1966 as a front for the MLN to carry out its more violent activities, along with many other similar groups, including the New Anticommunist Organization and the Anticommunist Council of Guatemala. These three groups operated within the United States supported government arm known as the Regional Telecommunications Center, which linked them to various government, military and police agencies. This network was built on the Committees against Communism created by the Central Intelligence Agency after the coup in 1954. The members of Mano Blanco were largely army officers, and the outfit received a lot of its funding from planters. It also received information from military intelligence. It was one of the only death squads directly affiliated with a political party. Most such groups were "phantom organizations," created so that the Guatemalan military could carry out illicit activities.

Armed with this support, Mano Blanca began a campaign described by the United States Department of State as one of "kidnappings, torture, and summary execution." One of the main targets of Mano Blanca was the Partido Revolucionario (PR), an anti-communist group that was the only major reform oriented party allowed to operate under the military-dominated regime. Other targets included the banned leftist parties. The PR drew a lot of its members from the activist base that had been created during the agrarian reform program begun by former president Jacobo Arbenz in 1952, and these individuals were targeted by the Mano Blanca. When it was founded, the group had the specific aim of preventing Méndez Montenegro from taking power. During the 1970s, Mano Blanca was led by Raúl Lorenzana.

Julio César Méndez Montenegro (November 23, 1915 – † April 30, 1996) was the Revolutionary Party President of Guatemala from July 1, 1966 to July 1, 1970. Mendez was elected on a platform promising democratic reforms and the curtailment of military power. The only civilian to occupy Guatemala's presidency during the long period of military rule between 1954 and 1986. Mendez had assumed the presidency under a pact in July 1966 that gave the armed forces carte blanche with respect to internal security matters and an effective veto over governmental policy. Nevertheless, his election and swearing in was considered a major turning point for the long military-led Guatemala. He was the first cousin of César Montenegro Paniagua whose kidnapping, torture and murder during the Julio César Méndez presidency is rumored to have been undertaken with presidential sanction.