present for duty at any time. The nation's officer corps still suffered from the promotion and retention of generals due to their political loyalties, not their professional abilities. Corruption and incompetence among officers was endemic, with some "raising it almost to an art form." Severe cutbacks in U.S. aid directly affected military performance. Artillery batteries previously allocated 100 rounds per day were reduced to firing only four daily. Each ARVN soldier was restricted to only 85 bullets per month. Because of fuel shortages and a lack of spare parts, sorties by South Vietnamese helicopter and cargo aircraft shrank by 50 to 70 percent. Due to President Thiệu's "no surrender of territory" command, the army was stretched to the limit defending terrain along a 600-mile frontier. Even the nation's strategic reserve, the Airborne and Marine Divisions, were occupied in static defensive roles. The ARVN, schooled by the Americans in rapid mobility and application of massive firepower, were losing the ability to deliver either. The military situation was exacerbated by the collapse of the South Vietnamese economy and a massive influx of refugees into the cities. During the same period, the North Vietnamese were recovering from losses incurred during the Easter Offensive of 1972 by replacing personnel and modernizing their equipment with a new influx of Soviet and Chinese military aid. During 1973, North Vietnam received 2.8 million metric tons of goods (worth $330 million) from communist-bloc countries, a 50 percent increase over the previous year. In 1974 that total increased to 3.5 million metric tons ($400 million) (according to CIA), while the South's aid was slashed to only $965 million per year, down from $2.2 billion. As a result, the number of artillery tubes within South Vietnam increased to 430, including new 122 mm and 130 mm guns, while armored forces were estimated to have increased to 655 tanks and armored personnel carriers, including the new Soviet-built BTR-60. PAVN By the end of 1974, the North Vietnamese General Staff had created two army corps headquarters, matching South Vietnam's command and control structure in the I and II Corps Tactical Zones. Most independent PAVN infantry regiments in the south were also combined into divisional structures. A U.S. Defense Attaché Office (DAO) (established in 1973 to replace MACV, the 50 officers and men of the DAO coordinated all military assistance to South Vietnam) report concluded that the PAVN had increased their strategic reserve