the actual war:
PODs for Franco losing are:
1. the republican government quickly reacts, has a plan and carries it out. for example, quickly arming the militant workers.
2. more bad luck: the general´s rising failed where it met staunch counter-measures, like in barcelona. if you know the hilarious story of general Queipo de Llano seizing control of Seville, this point needs no further explanation.
3. Outside help: no air assets from germany and italy, bringing over combat-ready forces from the Army of Africa after the majority of the fleet remained republican;
no helping hands from the Royal Navy for the nationalists (intelligence & lines of communication through Gibraltar), or backing of the rising through foreign bussiness interests. (the chairman of texas oil (?) personally diverted tankers en route to spain with a cargo already paid for by the government to nationalist held ports in the first days of the rising)
4. the propaganda war goes in favor of the left early
during the war.
- the leftist war effort was seriously hindered by the communist tendency to assume control and eliminating other leftist lunatics instead of sorting it out when the war was one.
- the communist give up their tendency to substitute tactics, and more generally, sound objective analysis, with propaganda. They insisted on repeating hopeless attacks which could not achieve anything because the press release was better.
- the anarchists... well, in short, they give up what anarchism is about. in a civil war, which is effectively a war between nation states which happen to represent the same nation, the war effort has to be planned, controlled and performed, you need clear hierarchical command structures- in short, everything the anarchists dislike becomes a cardinal virtue.