Prior to May 1937 political commissars were appointed by the party leadership - POUM , CNT etc. This was done in agreement with the central military committee of the party. Each battalion had a political commissar, and each company had a political delegate. The political commissars were equal in rank to the battalion commanders. Each order of the battalion commander had to be countersigned by the political commissar.

At a higher level was the brigade political commissar and then the divisional one and they were equal in rank to the brigade and divisional commanders.

The system was to draw the most politically and militarily experienced leaders. Their tasks were the military and political conduct of the war, security and jurisdiction at the front, the elimination of troops grievances, political education, the supply of mess provisions, control of troops' equipment, participation in military deliberations, regulation of leave etc. In short to maintain the political, moral and physical well being of the troops.

From May 37 onwards the Valencia government and their new supreme command ratified all new appointments for political commissars, although they were now to be referred to as war commissars.