Concerned by the emergence of Adolf Hitler in Nazi Germany, a group of left-wing politicians in France, led by Leon Blum, Edouard Daladier, Maurice Thorez, Edouard Herriot, Daniel Mayer, formed the Popular Front in 1934. Parties involved in the agreement included the Communist Party, the Socialist Party and the Radical Party.

In Spain left-wing groups followed the example set by France and established a coalition of parties to fight the national elections due to take place in February 1936. This included the Socialist Party (PSOE), Communist Party (PCE), Esquerra Party and the Republican Union Party. The Spanish Popular Front, as the coalition became known, advocated the restoration of Catalan autonomy, amnesty for political prisoners, agrarian reform, an end to political blacklists and the payment of damages for property owners who suffered during the revolt of 1934.

In the General Election held on 16th February, 1936 the Popular Front, won 263 seats out of the 473 in the Cortes and formed a new government. The Popular Front government immediately upset the conservatives by releasing all left-wing political prisoners. The government also introduced agrarian reforms that penalized the landed aristocracy. The Popular Front in France also did well in the May 1936 parliamentary elections and won a total of 376 seats. Leon Blum, leader of the Socialist Party, now become prime minister. Once in power the Popular Front government introduced the 40 hour week and other social reforms. It also nationalized the Bank of France and the armaments industry.

In July, 1936, José Giral, the prime minister of the Popular Front government in Spain, requested aid from France. The prime minister, Leon Blum, agreed to send aircraft and artillery. However, after coming under pressure from Stanley Baldwin and Anthony Eden in Britain, and more right-wing members of his own cabinet, he changed his mind. Baldwin and Blum now called for all countries in Europe not to intervene in the Spanish Civil War. In September 1936 a Non-Intervention Agreement was drawn-up and signed by 27 countries including Germany, Britain, France, the Soviet Union and Italy.

The Communist Party, that had originally supported the Popular Front government in France, now organized demonstrations against Blum's policy of non-intervention. With the left-wing in open revolt against the government and a growing economic crisis, Blum decided to resign on 22nd June. Maurice Thorez, the leader of the Communist Party in France, began to arrange the recruitment of soldiers to fight in the International Brigades for the Popular Front in Spain. The first group of volunteers left Toulouse on 29th July. The main recruitment centre was in Paris and from there they travelled by train to Perpignan. After spending the night in the town they were driven in trucks into Spain. Others went by sea via Marseilles.

The French supplied more men to fight with the Republican Army than any other country. Over 9,000 served, of whom some 3,000 were killed. It has been estimated that around half of all those who went were members of the Communist Party. The most prominent volunteer was André Malraux who organized a Republican air squadron. André Marty, another member of the French Communist Party, was responsible for their military training at Albacete. Over the next couple of years Marty developed a reputation as an officer willing to execute his own men if they showed signs of wavering in their communist faith or in their willingness to fight the enemy.

Only about 200 Frenchmen fought for the Nationalist Army. Most of these joined the Jeanne d'Arc Battalion led by Captain Bonneville de Marsangy. Jean Hérold-Paquis also served the Nationalists by broadcasting anti-Republican propaganda on Radio Saragossa. In January 1938 the French prime minister, Camille Chautemps, closed the frontier with Spain. This upset the Socialist Party and Communist Party and his government fell and was replaced by Leon Blum. When he began to argue for an end to the country's non-intervention policy, Neville Chamberlain and the Foreign Office joined with the right-wing press in France and political figures such as Henri-Philippe Petain and Maurice Gamelin to bring him down.

On 10th April 1938, Blum was replaced by Edouard Daladier, a politician who agreed not only with Chamberlain's Spanish strategy but his appeasement policy. On 27th February 1939, the French government recognized General Francisco Franco as the new ruler of Spain. The border was reopened and 236,000 refugees fled to France in an attempt to escape from the new fascist regime.