On 5 March 1939, the Republican Army, led by Colonel Segismundo Casado and the politician Julián Besteiro, rose against the socialist prime minister Juan Negrín, and formed a military junta, the National Defence Council (Consejo Nacional de Defensa or CND) to negotiate a peace deal.

[10] The Republican army still had between 250,000[11] and 500,000 men[3] but only 40 aircraft (three Natasha and two Katiuska bomber squadrons, and 25 Chatos and Moscas fighters),[12] little artillery and few automatic weapons.

[14] On 16 February, the high command of the Republican Army told Prime Minister Juan Negrín that further military resistance was impossible.

[17] Nevertheless, Negrín, backed by the communist PCE, wanted to continue fighting because Franco rejected giving any guarantee against reprisals and a continental war against fascism was believed to be imminent.

[20] Most noncommunist elements of the Popular Front in Madrid supported the plot, including one of the leaders of the PSOE, Julián Besteiro, because they believed that continuing the war was useless.

[26] On 5 March 1939, Colonel Segismundo Casado, supported by General Matallana, the CNT[27] (Cipriano Mera), the secret service of the Republic (the Military Investigation Service, Servicio de Investigación Militar, or SIM),[28] a section of the PSOE (Julián Besteiro) and a section of the UGT (Wenceslao Carrillo), deposed Negrín and formed a military junta, the National Council of Defence (Consejo Nacional de Defensa) in order to negotiate a peace deal with Franco.

[30] The other members of the junta were Casado, Julian Besteiro, Wenceslao Carrillo, Gonzalez Marín and Eduardo Val (CNT), Antonio Perez (UGT), and the Republicans Miguel San Andrés and Jose del Río.

[32] Ironically, Casado's justification for the coup was that Negrín and the PCE wanted to carry out a communist takeover, an identical justification to that of the Nationalist uprising, which began the Civil War, but in fact, he rose against the government because he wanted to negotiate peace and believed that removing Negrín and the communists was a precondition to negotiations with Franco.

[33] Casado had said to the commander of the Republican Air Force, Hidalgo de Cisneros: "I give you my word ... that I can obtain better terms from Franco than Negrín ever can.

[37] Nevertheless, Cipriano Mera's IV corps counterattacked and occupied Torrejón and Alcalá de Henares as the Nationalists started an offensive towards the Manzanares.

On 11 March, after days of bloody combat, Casado, backed by the IV corps of Cipriano Mera, defeated Barceló's troops.

In Ciudad Real, Escobar's Extremadura Army crushed the communist resistance led by the deputy Martínez Cárton.

Nevertheless, on 5 March, the Republican Navy (three cruisers and eight destroyers), led by Admiral Buiza, had fled to Bizerte after a Nationalist aerial bombardment.

[8] After the defeat of Barceló's troops, the council tried to start peace negotiations with Franco, hoping to achieve a guarantee against political reprisals.

On 12 March, the council proposed a peace deal with a guarantee against reprisals and a period of 25 days to allow anyone who wanted to leave Spain to do so.

[53][49][47] On 31 March, the Nationalists occupied Almeria, Murcia and Cartagena, controlling all Spanish territory except for an area of the port of Alicante, where thousands of Republicans expecting evacuation had assembled.

[59] Besteiro, still at his post in the basement of the Revenue Building at 7 Alcalá Street in Madrid, was arrested by the Nationalists when they entered the city and faced a court martial.