The Spanish Civil War began in 1936 and ended in 1939, during this war two camps opposed each other; The Republicans, defenders of the Second Spanish Republic, aided by the International Brigades and the Soviet Union, against the Nationalists led by Francisco Franco and supported by Nazi Germany and Fascist Italy. The war resulted from the failure of the nationalist uprising of July 17 and 18, 1936 against the government of the Second Spanish Republic.

This putsch is the culmination of the tensions generated by the Second Republic, which changed government 3 times, moving from left to right to return to the left during the elections of February 1936 where the Frente popular won the majority of votes. Strong tensions are created between the anarchists, the fascists and the parties of left/extreme left, leading to the putsch then to the civil war.

The People's Army of the Spanish Republic - name given to the land forces of the Second Spanish Republic after the reorganization of October 1936 - brought together the soldiers who had remained loyal to the Republic, the popular militias, and the volunteers from foreign countries, called the Brigades international. This all forming the republican camp, which also received material aid from the Soviet Union, France and the United Kingdom, opposing the nationalist camp. The latter received volunteers from Fascist Italy, called the Corpo Truppe Voluntarie and from the Condor Legion of Nazi Germany, as well as equipment from the latter.