De la wikipedia:
Las buenas intenciones de la II República se enfrentaron con la cruda realidad de una economía mundial recién salida de la crisis del 29, con una situación de creciente reivindicación de derechos para los trabajadores y con un paro creciente, lo que resultó en algunos casos en enfrentamientos callejeros, <B>revueltas anarquistas[/b], asesinatos por grupos extremistas de uno u otro bando, golpes de estado militares y huelgas revolucionarias. En España la agitación política tomó además un cariz particular siendo la Iglesia objetivo frecuente de la izquierda revolucionaria que veía en los privilegios de que gozaban una causa más del malestar social que se vivía. Lo que se tradujo muchas veces en la quema y destrucción de iglesias. La derecha conservadora, muy arraigada también en el país, se sentía profundamente ofendida por estos actos y veía peligrar cada vez más la buena posición de que gozaban ante la creciente influencia de los grupos anarquistas y comunistas.
Aunque le falta mencionar que grupos afines a Stalin organizaron matanzas de anarquistas. Y que si el bando republicano perdió la guerra, fue en gran medida por seguir masacrando anarquistas. No querían una guerra civil después de otra, así que iban allanando el terreno. Os recuerdo que los anarquistas no eran pocos, había al menos 3 millones afiliados a CNT/CGT.
De la Wikipedia en inglés:
During the Civil War, a reactionary Communist Party gained considerable influence due to the necessity of aid from the Soviet Union. Communists and "liberals" on the Republican side gave considerable effort to crush the anarchist revolution, ostensibly to bolster the anti-Fascist effort (the response was, "The revolution and the war are inseparable"). Pravda announced in December of 1936 that "...the mopping up of Trotskyists and anarcho-syndicalists has already begun. It will be carried out with the same vigor as in the USSR." Another communist boldly proclaimed in an interview that they would "make short work of the anarchists after the defeat of Franco." Their efforts to weaken the revolution were ultimately successful: hierarchy was eventually restored in many of the collectivized areas, and power was taken away from workers and unions, to be monopolized by the Popular Front.
Most important, perhaps, were the measures to destroy the militias, who were arguably leading the war effort in spirit as well as in action. The militias were eventually declared illegal and technically merged with the Popular Army. This had the effect of demoralizing the soldiers and taking away what they had ultimately been fighting for: not for the Soviet Union, but for themselves and for freedom. Vladimir Antonov-Ovseenko, working in Spain for Stalin, had predicted this in 1936: "Without the participation of the CNT, it will not, of course, be possible to create the appropriate enthusiasm and discipline in the people's militia/Republican militia."
Indeed, the counter-revolutionary fervor often served to weaken the anti-Fascist war effort. For example, a huge cache of arms was allowed to fall to Francoist forces for fear that it otherwise would end up in the hands of the anarchists. Troops were pulled off the front lines to crush anarchist collectives. Many able soldiers were assassinated for their political ideology; a leader of the repressive efforts, Enrique Lister, said that he would "shoot all the anarchists [he] had to." It was revealed that many anarchists were being held in prisons under Communist orders, rather than fighting on the front, and that furthermore many of these prisoners were tortured and shot.
Y a ver si dejáis de decir que el bando republicano defendía la república. La república en ese momento era inestable social y económicamente, sangrienta e incontrolable. Nadie con dos dedos de frente puede defender eso si no es habiendo sido mentido. Ambos bandos buscaban la estabilidad y el control, aunque fuera a costa de más sangre. Vamos, viendo cómo los comunistas luchaban contra los de su propio bando por ostentar el control debe ya daros una idea...