Armed and trained for this purpose, the Assault Guards was intended to provide a more effective force for internal security duties than the ordinary police or the conscription-based army.

Since its creation in 1844 the 25,000 strong Civil Guard had been available to be ordered into the larger cities in the event of unrest there, but this efficient rural force —its officers drawn from the regular army and with an oppressive image— was not seen as being in sympathy with the new Republic or particularly suited for urban operations.

The Ministro de la Gobernación Miguel Maura accordingly reorganized elements of the existing police into a more heavily armed republican security force for service in the cities, leaving the countryside to the Civil Guard.

This made a large number of serving soldiers decide to join this body; to avoid the misgivings and suspicions that military affiliation had created among the workers' militias.

The Assault Guards distinguished themselves as a reliable and shock infantry to which the Republic always entrusted its most delicate operations,[3] such as the battles of Madrid and Guadalajara, the securing of Belchite, and the suppression of the events in Barcelona during May.

On the other hand, in the Civil Guard the breakup of loyalists and rebels was distributed evenly at around 50%, although the highest authority of the corps, Inspector General Sebastián Pozas, remained loyal to the republican government.