Authors:

The communists basically acted as the police force of the security system of the [Spain] Republic and were very much opposed to the anarchists, partially because [Joseph] Stalin still hoped at that time to have some kind of pact with Western countries against [Adolf] Hitler. That, of course, failed and Stalin withdrew the support to the Republic. They even withdrew the Spanish gold reserves.

Source: thehumanist.com
The communists basically acted as the police force of the security system of the [Spain] Republic and were very much opposed to the anarchists, partially because [Joseph] Stalin still hoped at that time to have some