Just because something is good does not mean that it will survive.
For example, the Warsaw Ghetto uprising against the Nazis failed but that does not mean that the uprising was a bad cause or that the Nazi regime was correct, far from it. Similarly, while the experiments in workers' self-management and communal living undertaken across Republican Spain is one of the most important social experiments in a free society ever undertaken, this cannot change the fact that Franco's forces and the Communists had access to more and better weapons.
Faced with the aggression and terrorism of Franco, and behind him the military might of Fascist Italy and Nazi Germany, the treachery of the Communists, and the aloofness of the Western bourgeois "republics" (whose policy of "non-intervention" was strangely ignored when their citizens aided Franco) it is amazing the revolution lasted as long as it did.
This does not excuse the actions of the anarchists themselves. As is well known, the C.N.T. co-operated with the other anti-fascist parties and trade unions on the Republican side (see next section). This co-operation lead to the C.N.T. joining the anti-fascist government and "anarchists" becoming ministers of state. This co-operation, more than anything, helped ensure the defeat of the revolution. While much of the blame can be places at the door of the would-be "leaders," who like most leaders started to think themselves irreplaceable and spokespersons for the organisations there were members of, it must be stated that the rank-and-file of the movement did little to stop them. Most of the militant anarchists were at the front-line (and so excluded from union and collective meetings) and so could not influence their fellow workers (it is no surprise that the "Friends of Durruti" group were mostly ex-militia men). However, it seems that the mirage of anti-fascist unity proved too much for the majority of C.N.T. members (see section I.8.12).
Some anarchists still maintain that the Spanish anarchist movement had no choice and that collaboration (while having unfortunate eeffects) was the only choice available. This view was defended by Sam Dolgoff and finds some support in the writings of Gaston Leval, August Souchy and many other anarchists. However, most anarchists today oppose collaboration and think it was a terrible mistake (at the time, this position was held by the majority of non-Spanish anarchists plus a large minority of the Spanish movement, becoming a majority as the implications of collaboration became clear). This viewpoint finds its best expression in Vernon Richard's Lessons of the Spanish Revolution and, in part, in such works as Anarchists in the Spanish Revolution by Jose Peirats and Anarchist Organisation: The History of the F.A.I by Juan Gomaz Casas as well as in a host of pamphlets and articles written by anarchists ever since.
So, regardless of how good a social system is, objective facts will overcome that experiment. Saturnino Carod (a leader of a C.N.T. Militia column at the Aragon Front) sums up the successes of the revolution as well as its objective limitations:
"Always expecting to be stabbed in the back, always knowing that if we created problems, only the enemy across the lines would stand to gain. It was a tragedy for the anarcho-syndicalist movement; but it was a tragedy for something greater — the Spanish people. For it can never be forgotten that it was the working class and peasantry which, by demonstrating their ability to run industry and agriculture collectively, allowed the republic to continue the struggle for thirty-two months. It was they who created a war industry, who kept agricultural production increasing, who formed militias and later joined the army. Without their creative endeavour, the republic could not have fought the war . . ." [quoted by Fraser, Blood of Spain, p. 394]