After the ruling centre-right coalition collapsed amid the Straperlo corruption scandal, new elections were scheduled. Two wide coalitions formed: the Popular Front on the left, ranging from Republican Union to Communists, and the Frente Nacional on the right, ranging from the centre radicals to the conservative Carlists. On 16 February 1936, the left won by a narrow margin.
On 12 June, Prime Minister Casares Quiroga met General Juan Yagüe, who falsely convinced Casares of his loyalty to the republic. Mola began serious planning in the spring. Franco was a key player because of his prestige as a former director of the military academy and as the man who suppressed the Asturian miners' strike of 1934. He was respected in the Army of Africa, the Army's toughest troops. He wrote a cryptic letter to Casares on 23 June, suggesting that the military was disloyal, but could be restrained if he were put in charge. Casares did nothing, failing to arrest or buy off Franco.
With the help of the British Secret Intelligence Service agents Cecil Bebb and Major Hugh Pollard, the rebels chartered a Dragon Rapide aircraft (paid for with help from Juan March, the wealthiest man in Spain at the time) to transport Franco from the Canary Islands to Spanish Morocco. The plane flew to the Canaries on 11 July, and Franco arrived in Morocco on 19 July.
On 12 July 1936, Falangists in Madrid killed police officer Lieutenant José Castillo of the Guardia de Asalto (Assault Guard). Castillo was a Socialist party member who, among other activities, was giving military training to the UGT youth. Castillo had led the Assault Guards that violently suppressed the riots after the funeral of Guardia Civil lieutenant Anastasio de los Reyes. (Los Reyes had been shot by anarchists during 14 April military parade commemorating the five years of the Republic.)
From 24 July a coordinating junta was established, based at Burgos. Nominally led by Cabanellas, as the most senior general, it initially included Mola, three other generals, and two colonels; Franco was later added in early August.
In July 1936, British officials convinced Blum (the prime minister) not to send arms to the Republicans and, on 27 July, the French government declared that it would not send military aid, technology or forces to assist the Republican forces. However, Blum made clear that France reserved the right to provide aid should it wish to the Republic: "We could have delivered arms to the Spanish Government [Republicans], a legitimate government... We have not done so, in order not to give an excuse to those who would be tempted to send arms to the rebels [Nationalists]."
On 1 August 1936, a pro-Republican rally of 20,000 people confronted Blum, demanding that he send aircraft to the Republicans, at the same time as right-wing politicians attacked Blum for supporting the Republic and being responsible for provoking Italian intervention on the side of Franco.
However, the Blum government provided aircraft to the Republicans covertly with Potez 540 bomber aircraft (nicknamed the "Flying Coffin" by Spanish Republican pilots), Dewoitine aircraft, and Loire 46 fighter aircraft being sent from 7 August 1936 to December of that year to Republican forces.
The Republic proved ineffective militarily, relying on disorganised revolutionary militias. The Republican government under Giral resigned on 4 September, unable to cope with the situation, and was replaced by a mostly Socialist organisation under Francisco Largo Caballero. The new leadership began to unify central command in the republican zone.
On 21 September it was decided that Franco was to be commander-in-chief (this unified command was opposed only by Cabanellas), and, after some discussion, with no more than a lukewarm agreement from Queipo de Llano and from Mola, also head of government. Emilio Mola y Vidal, 1st Duke of Mola, Grandee of Spain was one of the three leaders of the Nationalist coup of July 1936, which started the Spanish Civil War.
On 21 September, with the head of the column at the town of Maqueda (some 80 km away from Madrid), Franco ordered a detour to free the besieged garrison at the Alcázar of Toledo, which was achieved on 27 September.
On the Nationalist side, Franco was chosen as chief military commander at a meeting of ranking generals at Salamanca on 21 September, now called by the title Generalísimo.
On 1 October 1936, General Franco was confirmed head of state and armies in Burgos. A similar dramatic success for the Nationalists occurred on 17 October, when troops coming from Galicia relieved the besieged town of Oviedo, in Northern Spain.