From what I can tell, the International Brigades were mostly
effective only for propaganda purposes and to camouflage the
presence of Soviet assistance to the Republican government. The
32,000-35,000 men in the brigades were a grab bag of unemployed
workers, middle class non-combatants, veterans from the first
world war, etc; all motivated by a shared socialist ideology and
anti-fascist outlook. Despite their generally noble intentions
(a few were certainly adventure seekers), they were mostly
unused to combat and lacked military training [2006, Beevor].
This was a problem given that one of the motivations of the
International Brigades were to provide an example in military
discipline and tactics to the equally unready Republican army.
Soviet military advisors tried to provide adequate training to
the brigades, but often ran into problems such as political
squabbles between soviet and republican leaders, cultural
differences, and varying quality of equipment (which was mostly
poor). The International Brigades