The supremacy of the Fifth Air Force in the skies over Korea forced the North Koreans in the first month of the war to resort to night movement of supplies to the battle area. They relied primarily on railroads to move supplies to the front, however a shortage of trucks posed the most serious problem of getting supplies from the trains to individual units, forcing them to rely on carts and pack animals. The KPA was able to maintain transport to its front lines over long lines of communications despite heavy and constant air attacks. The UN air effort failed to completely halt military rail transport. Ammunition and motor fuel, which took precedence over all other types of supply, continued to arrive at the front, though in smaller amounts than before. At best there were rations for only one or two meals a day. Most units had to live at least partially off the South Korean populace, scavenging for food and supplies at night. By September 1 the food situation was so bad in the KPA at the front that most of the soldiers showed a loss of stamina with resulting impaired combat effectiveness.