A potential opposition force was the Mexican Federal Army. Troops were often men forced into military service and poorly paid. Díaz increased the size of the military budget and began modernizing the institution along the lines of European militaries, including the establishment of a military academy to train officers. High rank officers were brought into government service. Díaz expanded the crack police force, the "Rurales", who were under control of the president. Díaz knew that it was crucial for him to suppress banditry; he expanded the "Rurales", although it guarded chiefly only transport routes to major cities. Díaz thus worked to enhance his control over the military and the police.