The Francoist military rebellion of July 1936 failed in Barcelona, and since then the city, as well as the rest of Catalonia, had been under the control of workers' militias, especially ones associated with the anarchist trade union Confederación Nacional del Trabajo (CNT-FAI) and the socialist trade union Unión General de Trabajadores (UGT).

Just after taking the last rebelling barracks, the anarchist leaders met with the President of the Generalitat de Catalunya Lluis Companys.

The Generalitat and the central government had lost all freedom of action and assisted passively in the revolution that was taking place in Catalonia and extended to Aragon.

Tension in the streets of Barcelona was becoming evident of the arrival of a hot spring: the Patrullas de Control were led by José Asens and continued arbitrarily arresting and murdering in their infamous paseos.

Josep Tarradellas, as Companys' right hand, was determined to unify the security forces in Catalonia under one command and to finish with the Patrullas de Control.

The open crisis forced Companys to give in to their demands, anarchists retained their weapons, and the Control Patrols remained in place.

Although the PSUC was not a bourgeois party, from the point of view of the Republican authorities it presented itself as an alternative to the revolutionary chaos, and it advocated for the strengthening of central government that would replace the local committees.

Orwell summarized the PSUC-party line as follows: Clinging on to the fragments of workers' control and parroting revolutionary aims is worse than useless: not only an obstacle but also counter-revolutionary, because it leads to divisions that fascists can use against us.

[9]On the position of the POUM, shared by most of the more radical anarchists, like the Friends of Durruti,[10] Orwell states: The workers' militias and police-forces must be preserved in their present form and every effort to "bourgeoisify" them must be resisted.

[12] A force of 200 police officers, commanded by the Minister of Public Order of the Government of Catalonia, Eusebio Rodríguez Salas, went to the Telefónica central exchange and presented itself at the censorship department located on the second floor, with the intention of taking control of the building.

Rodríguez Salas, on his part, had authorization from the head of internal affairs of the regional government, Artemi Aiguader i Miró.

Eroles persuaded the CNT workers to cease fire; although they resisted at first, they surrendered their weapons, not before shooting through the windows to empty their ammunition.

[13] The POUM, the Friends of Durruti Group, the Bolshevik-Leninists and the Libertarian Youth took positions, and after a few hours all of the political parties had taken out the weapons that they had hidden and began building barricades.

In the city centre, where the headquarters of trade unions and political parties (installed in requisitioned buildings and hotels) were relatively close, shooting began, and cars circulating were machine-gunned.

Meanwhile, the anarchists Joan García Oliver and Federica Montseny launched an appeal on the radio to ask their followers to lay down their weapons and return to their jobs.

[16] On the Aragon front, units of the 26th Anarchist Division (former Durruti Column) under the command of Gregorio Jover, gathered in Barbastro to march on Barcelona.

At 9:30 the Assault Guard attacked the seat of the doctors' trade union in Santa Ana Square, in central Barcelona, and the headquarters of the local FIJL.

The Friends of Durruti Group published various leaflets demanding the release of Francisco Maroto del Ojo, an Andalusian anarchist who had recently been jailed, and asking people to resist.

At about five o'clock, the anarchist authors Camillo Berneri and Francesco Barbieri were arrested by a group of twelve guards, six of them members of the local police and the rest from the PSUC.

[note 3] In fact, the British feared that anarchists would take control of the situation, and talks occurred on evacuating foreign subjects from the city.

[20] At night, Federica Montseny, Minister of Health and an important member of the CNT, arrived with the purpose of mediating between all of the parties.

[20] The Communist Antonio Sesé, General Secretary of the Catalan UGT and a member of the Generalitat's new provisional council, died in a gunfight on his way to receive his new appointment.

[20] At night, Lluis Companys and then Prime Minister Francisco Largo Caballero held a telephone conversation in which the Catalan President accepted the Spanish government's offer of assistance for restoring order.

"[20] The expeditionary forces that entered Barcelona were under the command of Lieutenant Colonel Emilio Torres, who enjoyed certain sympathy from anarchists.

[22] Assault Guards in Barcelona, Tarragona and many other cities proceeded to disarm and arrest numerous members of the CNT, FAI, Libertarian Youth and POUM who had taken part in the riots.

The Generalitat of Catalonia was restored to its old functions with the entry of one representative of the UGT (the communist Vidiella), one of the CNT (Valerio Mas) and one of ERC (again Tarradellas).

The new Director of Public Order in Barcelona, José Echevarria Novoa, soon restored normality in much of the judicial system,[26] but in that way, the communists could take more easily their crusade against the POUM.

The POUM situation was quite different, as the republican government soon outlawed the party, on 16 June, and arrested its main leaders, including Julián Gorkin and Andreu Nin.

[30] The Spanish Netflix drama Cable Girls (2017) also portrays a dramatization of events of the May Days but is set in Madrid instead of Barcelona.