‘Italy and Germany did a great deal for Spain in 1936 … Without the aid of both countries, there would be no Franco today’, said Adolf Hitler to Galeazzo Ciano, the Italian Minister of Foreign Affairs and son-in-law of Benito Mussolini, in September 1940. It is an opinion that sums up perfectly what many contemporaries believed then, and studies have confirmed decades later: that the German and Italian intervention had been decisive in the defeat of the Republic or the victory of the rebel officers who rose against it July 1936.

Some historians, however, believe that the international intervention was not so decisive, and that the causes are to be found in the characteristics of the two armies – Franco's was better – and in their policies, which is usually summed up as the ‘unity’ of the national zone and republican ‘discord’. Political, military and international causes would thus summarise the essence of complex explanations that would answer the simple question as to why the Republic lost the war.

The international situation ‘determined’ the course and outcome of the civil war. That is the conclusion of Enrique Moradiellos when he assesses all that he and other researchers, including Ángel Viñas, Robert Whealey, Paul Preston, Walther L. Bernecker, Gerald Howson and Pablo Martín Aceña, have written on this subject. Without the aid of Hitler and Mussolini, ‘it is very hard to believe that Franco could have won his absolute and unconditional victory’, and ‘had it not been for the suffocating embargo imposed by non-intervention and the resulting inhibition shown by the western democracies, it is very unlikely that the Republic would have suffered an internal cave-in and such a total and merciless military defeat’.