Martínez began his military career in the Salvadoran Army, attended the Polytechnic School of Guatemala [es], and attained the rank of brigadier general by 1919.

The 1931 coup and Martínez's succession to the presidency allowed for the rise of a series of military dictatorships that held onto power in El Salvador until 1979.

He was promoted to captain major that same year during the Third Totoposte War against Guatemala, where he fought under former Salvadoran president and Brigadier General Tomás Regalado.

[1] As set out in the constitution of El Salvador, the Legislative Assembly convened on 12 February 1931 to select a president, and the legislature unanimously voted in favor of declaring Araujo the election's winner after he promised to reimburse the campaign costs for two other presidential candidates – Alberto Gómez Zárate and Enrique Córdova – in order to satisfy them and their supporters in the legislature.

[18] Ongoing economic problems caused by the Great Depression and the unrest that followed persisted through Araujo's presidency, leading to Martínez using his position as minister of war to quell protests.

[27] Joaquín Castro Canizales [es], a Salvadoran poet and journalist, told American historian Thomas P. Anderson that Martínez had no advanced knowledge that the coup would occur but that he did know that many military officers were dissatisfied with Araujo's government.

[23] Meanwhile, in a 1968 interview, Araujo himself stated that "it was General Martínez who secretly directed the move that brought him to power [...] I do not believe that other members of the my government, honorable men, were involved".

[29] The Estrella Roja newspaper of the Communist Party of El Salvador praised the coup as "heroic and necessary" but also voiced concern that Martínez would not be able to solve the country's economic crisis.

[53] On 15 January, the Guatemalan government arrested communist leader Juan Pablo Wainwright for supposedly planning to launch a revolution in Central America.

[56] On 22 January 1932, thousands of peasants led by Francisco Sánchez [es] in western El Salvador—armed with sticks, machetes, and "poor quality" firearms—launched a rebellion against Martínez's government.

[57] A group of indigenous Salvadorans known as the Pipils, led by Feliciano Ama, joined the communist rebels because they were sympathetic to their ideology and believed that victory was assured.

[58][59] Communist and Pipil rebels attacked and captured the towns and cities of Colón, Jayaque, Juayúa, Izalco, Nahuizalco, Salcoatitán, Sonzacate, Tacuba, and Teotepeque.

In the manifesto, he stated that it was necessary to "suffocate [the rebels] with a strong hand" ("sofocarlos con mano fuerte") and promised to restore peace and constitutional order.

In January 1932, Martínez appointed Miguel Tomás Molina as his minister of finance in an effort to establish confidence in the country's financial stability and integrity.

[87] On 23 February 1932, the Salvadoran government suspended repayments of a 1922 loan from American and British lenders, in part because of Martínez's frustration with failing to receive recognition from the United States shortly after he assumed power.

[91] The "Martínez Doctrine" was temporarily suspended in December 1941 during World War II in order for El Salvador to benefit from the Lend-Lease Act, that was promoted by the United States.

The bank had the exclusive right to print money, import and export gold, and control foreign exchange rates; it pegged the Salvadoran colón at 2.5 colones to the United States dollar.

Several government officials, such as Molina, Brigadier General Manuel Castaneda, Doctor Maximiliano Brannon (sub-secretary of finance), and Augustín Alfaro (chief audit officer), resigned their positions in protest at Martínez's announcement, accusing him of continuismo.

The constitution prohibited the possession of firearms, explosives, and bullets; the consumption of alcoholic beverages and tobacco; and the usage of matches and all types of fossil fuel.

[125] In mid-1938, Fay Allen Des Portes, the United States ambassador to Guatemala, told Hull that he had received reports that Martínez had "turned Fascist in the letter and the spirit".

[129] In 1936, Martínez's government was among the first to recognize Francisco Franco as the legitimate ruler of Spain during the Spanish Civil War,[126] even before Germany and Italy had done so.

The air force initially attempted to purchase the bombers from North American Aviation, but the company refused to accept coffee as payment.

[140] Beginning in 1940, he began to crackdown on Nazi activity in El Salvador[141] and even suppressed a fascist demonstration based on the Italian Blackshirts on 10 June 1940, the day that Italy joined World War II on the side of the Axis powers.

[144] After the outbreak of World War II, Salvadoran exports to Germany diminished significantly, pushing El Salvador to form closer economic ties with the United States.

[105] In August 1943, some opposition politicians, military officers, and anti-fascist activists began plotting to overthrow Martínez, but several of the plotters were arrested in late 1943.

[150] The rebel military factions occupied strategic locations in San Salvador and in other major cities and took control of the air force and the YSP radio station.

[153] After the United States ambassador to El Salvador demanded to know the circumstances surrounding Wright's death,[155] Rodolfo Morales, the minister of governance, resigned.

[158] He returned from exile in 9 July 1955, meeting President Óscar Osorio when his plane landed in San Salvador, but was greeted by protests.

[175] Jorge Lardé y Larín, a Salvadoran historian and professor at the Captain General Gerardo Barrios Military School, criticized Martínez and his government in his published works, emphasizing that he was not a hero.

[177] More recently, historians Héctor Lindo Fuentes, Erik Ching, and Rafael Lara Martínez wrote that those same conservatives "might have cared little" about the mass killings during the anti-communist Matanza.