 Complete the following phrase:  Finally, the Communist-led Antifascist Worker and Peasant Militias MAOC formed five battalions that took an active part in the Siege of Cuartel de la Montaña on 20 July 1936. One of these battalions became the Fifth Regiment 5o Regimiento de Milicias Populares, a military unit intended as a model for other military units to follow in the initial chaotic period of the civil war. Its first commander was Enrique Castro Delgado. Later the Fifth Regiment would take an active part in the battles of Somosierra and 