In September of 1926, the Mexican military, at first just under General Miguel Pina, made preparations to use the mitrailleuse against the Yaqui people in Sonora, then led by their military chief Luis Matus (Matius in some later accounts), and his lieutenant, Albin Cochemea. The 1st, 8th, and 18th infantry battalions prepared to bring a more modern state of warfare against the indigenous inhabitants of Vicam and other Yaqui pueblos along the river. By October 5th, after intense fighting, the remaining Yaqui soldiers had retreated to the mountains above the river, and the Mexican forces decided to mount a vast offensive against them. More than 12,000 Mexican Federal troops, under the command of General Obregon, General Abundio-Gomez, and General Manzo, directed the operations against the remaining Yaqui forces, using munitions that included 8mm mitrailleuse, and aeroplanes carrying gas asphyxiants.