As part of the army of Colonel Gertrudis G. Sánchez, whose forces Arrieta's had joined, Amaro fought against the Zapatistas in Morelos, engaging them at least nineteen times. In one of these engagements, the battle of Jojutla de Juárez, he earned the ""Cruz de Segunda Clase"," a heroism medal. From 1913 to 1914, he fought the federal troops under the command of Victoriano Huerta, continuing all the while to rise in rank. By 1914 he had risen to the rank of general.