Spain affected the course of events in the crucial second half of the 1930s by becoming the major political and military testing ground. Spain provided the invaluable military and political experience in such matters as a role of aviation and artillery in modern war (tanks hadn’t won their spurs yet), relationship between the front line and rear, etc. Not always that experience was apprehended, and partly it became outdated with the beginning of the Second World War and its blitzkriegs. Military experts of the USSR and France could make sure that a «war of motors» might be a positional war — as the First World War was. It led to tragic mistakes in 1940–1941.

The beginning of the Civil War, distribution of arms among civilians in the Republic led to the beginning of not just a socio-political, but deep social revolution, qualitative changes in property relations and the political system. As a result of industrial collectivization (incautation, socialization) in Spain, first of all in Catalonia and Aragon, a new sector of economy appeared that qualitatively differed both from the capitalist ones, and from the state ones — first of all by the advanced system of industrial democracy, participation of a worker in taking industrial decisions. The negative attitude of the anarchist doctrine to the «democracy» as to the multi-party parliamentary system didn’t prevent anarcho-syndicalists from incorporating democracy in the sphere of production. Relying on the trade-union structures, the аnarcho-syndicalists and the left socialists made a practical step to divorce a producer from the means of production. But it was just a step.

The dictatorship of the manager was replaced by the power of the collective represented by its core group (first of all trade-union leaders from CNT structure) and almost religious influence of anarchist slogans, contradiction with which could be considered the counterrevolution. However, the influence of the ideology shared by the significant mass of workers played the role of mobilizing the masses including at the place of production. The anarcho-syndicalists and the left socialists managed to create a rather effective and democratic social system (to the extent possible in the conditions of Civil War) based on the industrial democracy. Despite the heavy economic situation caused by war and split of the country, the collectivized industry prevented a steep decline in production. Introduction of industrial democracy system drove the productive efficiency which after all might be possible at the Spanish enterprises of the day in conditions of war and partial economic blockade. A myth about «disorganization of production by anarcho-syndicalists» could be considered completely wrong. When the workers and engineers took possession of factories, they did their best. The production volumes required to meet war demands exceeded the pre-war performance. However, the model of self-government and industrial democracy to be coordinated by trade unions and semi-government public structures dissatisfied the representatives of other political forces. In 1937 it resulted in a considerable aggravation of political struggle in the republican camp. The struggle against the industrial democracy which took place during Negrin’s government (1937–1939) contributed to a decline in the economic growth rate in comparison to the Largo Caballero governance.

The rural collectivization initiated by anarchists also received wide expansion within the Republic. Unlike in the USSR, it had not been caused by governmental pressure upon the peasantry. In some cases the majority of peasants forced minority to collectivization, in the other cases individual farms were preserved. Sometimes the radical anarchist detachments compelled most peasants to join collective farms, but CNT and leaders of anarcho-syndicalists opposed it. The general support for collectivization and its voluntary character for the majority of peasants were also confirmed by the fact that after defeat of anarcho-syndicalists in the conflict with communists in May-August, 1937, when anarchists had already no opportunity to lay violent hands on their opponents, the mass movement of agrarian collectives continued and even extended. As a whole, the collectivization produced a good effect on a nationwide scale as well. In spring 1937 the food situation noticeably improved, the cropland acres were extended which was admitted even by the opponents of anarchists. Successes and failures of particular collectives depended on their leaders, but as a whole, the movement which liquidated a tax burden without prior arrangements, latifundium system and small-scale crofting agriculture demonstrated its sustainability.

From September 1936 till May 1937 the F. Largo Caballero government of the Republic promoted deep social transformations. The anarcho-syndicalists participated in it since November and therefore it was not just a government of the People’s Front, but of a wide anti-fascist coalition. The activity of anarchist ministers in the government did not basically have just any specifically anarchical, but all-democratic character and fitted in the framework of the social state. While CNT was in the government, the opponents of anarcho-syndicalist social and economical experiment could not develop a serious attack against the industrial democracy sector. As soon as CNT left the government, they launched an attack which resulted in the essential curtailing of the social revolution. The presence of CNT in the government was a condition for preservation of those revolutionary achievements which had been reached in autumn of 1936. After syndicalists had joined the government of Spain, they conducted relatively pluralist economic policy which was supported by Largo Caballero and in fact became the basis of the social and economic line of the cabinet, as a whole.

During the Largo Caballero governance the military construction of the Republic was based on a combination of militia principles at a level of divisions and those of regularity at a level of units. That combination didn’t insure the Republic against a defeat in Malaga, but enabled to defend Madrid and to win the Italian corps near Guadalajara. The Negrin-Prieto government began to destroy the militia system, but didn’t gain a victory in the war. The decline in soldiers’ enthusiasm and growth of caste as well as a lack of control over officers contributed to the decrease in combat proficiency of the republican army in the second half 1937 and its defeats. Toppling of Largo Caballero frustrated the preparation of operation in Extremadura which could force the war from the positional phase which was fatal for the Republic.

Infighting more characteristic of the Republic than of Franco regime was not by itself dangerous to the Republic. Only during the short moments it could pose a threat to the front line, and Franco didn't take advantage of the opportunity. The internal political conflicts had a negative impact on the destiny of the Republic not so much through their course, as through their outcome in May 1937.

In the first half of 1937 the underlying contradictions built up in republican camp. The communists were opposing the revolution which had burst in Spain, they believed that the revolution broke away from the Soviet pattern they tried to achieve and also prevented a victory of the Republic. With regard to the latter assumption they saw eye to eye with Azaña, Prieto and Negrin. The political center of Republic veered to the right, the communists became the center of consolidation of the Party of Order which opposed the social revolution. Largo Caballero was on side of the revolution which took place in Spain because he considered it a tool of mass mobilization required for a victory over fascism and because the revolution assigned a clear meaning to the struggle — a victory of a new society over an old one and not just preservation of Spain which had existed up to 1936. Largo Caballero and its supporters sought a model of the new society which would develop during the revolution and would match the principles of democratic socialism. After they got acquainted with the ideas defended by the syndicalists in the government, the caballerists began to incline to an idea to create a society which basic structure would comprise workers’ trade-unions.