On May 3, 1937 PSUC and Catalan nationalists provoked the armed conflicts with anarcho-syndicalists in Barcelona which were announced «an anarcho-trotskyst rebellion». In spite of the fact that the parties managed to reach the cease-fire agreement, the conflicts of May 3–6 were used by the opponents of CNT and POUM to establish control over Barcelona and begin reprisals against opposition. But for as long as Largo Caballero government had the power, the investigation of events in Barcelona could result in the discredit of PSUC and communists as a whole. Therefore, the prompt overthrow of Largo Caballero, who disagreed with the interpretation of conflicts as the anarcho-trotskyst rebellion, became a matter of principle for the communists. Thus, the overthrow of Largo planned by the communists as early as in March became an immediate task in May. On top of that, the CPS was ready to keep Largo as a formal head of the government provided that a real power and, first of all, the control over force structures would be concentrated in the hands of the block communists and PSOE «centrists».
The communists struggled to change the governmental strategy and military policy not limiting themselves, if necessary, to the overthrow of the head of the government in power. However, it did not mean that they planned all course of the May political crisis in advance starting from armed conflicts in Barcelona. They were ready to operate resolutely and roughly winning back a position by position from their opponents, but when their actions in Barcelona caused discontent, they were even taken aback in the first moment. Moreover, the result of their actions in Barcelona did not guarantee to the communists the crushing defeat of the opponents and even placed their own positions under a threat. In the circumstances concerned the communists were actually saved by leaders of the PSOE right wing and President Azaña. It resulted in a new division of powers where positions of communists were not yet certainly dominating though rather strengthened. The communists could take advantage of another, less risky occasion to advance in transforming the Spanish Republic into the «national democracy». They were not almighty manipulators; their force involved the other thing — the consistency with which they headed in the direction of 1'etatisation pulling PSOE l’etatists along after themselves.
After the May events, Largo Caballero could continue to head the government upon one of two conditions: either he would yield to dictation and turn into a nominal figure or would take advantage of an unfavorable role of PSUC in the events in Barcelona and weaken the communists and create the government on a new trade-union basis (having balanced GWU and CNT in the rights) and ignoring the president’s opinion appeal to the organized masses. It, certainly, once again would break up the Constitution, but after July 18 it had been broken quite often. Such is Revolution. It was one of the crucial points in the development of the Spanish Revolution, so also of the world. Would there be a new syndicalist model which would exist alongside with American, Soviet and fascist variants of the regulated industrial society? Would the countries taking the path of a social state face a dilemma: to create a new society on the basis of authoritarianism, capitalist pluralism or, as in Spain, on the basis of industrial democracy?
It is obvious that the government which core group would consist of trade-union leaders of CNT and GWU would continue the social transformations focused on the improvement of collectivization and syndicalisation. Such government would investigate the events in Barcelona in the way unfavorable for communists, which could result in slackening of communists in the force structures as well, and at the end of the day — defeat of CPS in the race for power. However, the same course of events meant the overthrow of not only communists, but also of the right socialists and republicans. But in May 1937 Largo Caballero didn’t dare to operate revolutionary. «Spanish Lenin» did not enjoy determination of true Lenin. At the same time, Largo Caballero gave up a role of figurehead of a ship which suddenly altered the course line.
As he didn’t dare to break up with the party-presidential system, Largo Caballero failed, and on May 17 M. Azaña charged a socialist J. Negrin focused on the closest cooperation with CPS with the formation of a new government. The political upheaval was prepared in spring 1937 not in favor of figures, but in favor of the communists block and the right wing of socialists. The social-liberal and communist politicians fixed upon Negrin as the most convenient compromise figure.
Emissaries of Comintern directly participated in such manipulations and were a force in a coalition of «May winners». It was obvious that the right socialists couldn’t have triumphed over Largo Caballero and the social revolution, if they hadn’t obtained communist support.
Anti-fascists had more than one (external), at least two factors of resistance (which had been already proved by the defense of Madrid) — the revolution and assistance of the USSR. It was impossible to win at that conjuncture, having only one of them. The defeat resulted from not only the weakening of Soviet assistance, but of the revolution as well. Having paralyzed the revolution, the new Spanish government killed incentives of dedicated struggle for a victory. Largo Caballero could combine both such power sources of the Republic. Negrin gave up on one of them following which only the outbreak of the Second World War could save the Republic from ruin.
Up to 1938, the Soviet assistance counterbalanced the material and technical intervention of Germany and Italy, and the inter-brigades — partly the presence of the Italian military contingent. In the end of 1937 the Soviet assistance began to decline, while fascist assistance began to increase. The declining of the Soviet assistance was connected with disappointment of the Soviet government over inability of the new Negrin — Prieto government to achieve the promised breakdown in the war and complication of the international situation when the Spanish problem became less important in comparison with crises in China and Czechoslovakia.
From the second half of 1937 the Soviet assistance was provided to China as well, and the supplies to the East «were subtracted» from the supplies that the USSR could direct to Spain. China was more important yet for the USSR, than Spain — in fact this time the struggle was developed in immediate proximity from the Soviet borders. The peripheral containment of Japan was critical for the USSR during all the 1930s.
In spring-summer 1937 Republicans had an opportunity to recapture the initiative when Franco carried on a two-front war having concentrated forces in the North. Instead of focusing efforts on the victory and preparation of the offensive operation, the communists and social-liberals passionately struggled for power, and the Republic wasted time. In summer they conducted an operation angled towards their style, and it became clear that their methods were not better, but worse than Largo Caballero's war. In July-December, 1937 the chance to recapture the initiative was missed.
Nevertheless, the USSR continued to support the Republic which preservation (even without chance to win) drew Germany and especially Italy away from operations in the east of the Europe.
Handling the assistance that depended on a complex foreign policy situation, Stalin did not discontinue the struggle in Spain and strengthening of the control over the political system of the Republic. As experience of people’s democracies showed, when establishing communist regimes Stalin acted step by step even in much more favorable conditions.