Shortly after the Spanish coup of 17 July 1936, the MAOC formed five battalions that took an active part in the defence of Madrid. One of these battalions eventually became the renowned "Fifth Regiment" ("5º Regimiento de Milicias Populares"), a military unit directly supported by the Communist Party of Spain and intended as a model for other military units in the initial chaotic period of the civil war. In the first critical phase of the war the Communists and Socialists led the implementation of a policy that sought to replace the spontaneous and disorganized bands fighting for the Spanish Republic with loyal, disciplined and militarized units. Thus the MAOC members eventually became integrated in different units of the Spanish Republican Army and their militia became extinct.