Sa'udi Arabia's armed forces totaled active 124,500 personnel in 2002, not including the 75,000 members of the national guard. The army had 75,000 personnel, 1,055 main battle tanks, and an army aviation command. The navy's strength was 15,500 personnel including 3,000 marines. The navy was equipped with 4 frigates and 26 other combatants. The air force had 18,000 personnel and manned 294 combat aircraft. The national guard, numbering 75,000, is used chiefly for internal security and is an elite strategic reserve loyal to the Royal family. Sa'udi Arabia also had a 10,500-member frontier force, a 4,500-member coast guard, a helicopter-equipped counterterrorist unit, and 7,000 foreign military personnel under contract from members of the GCC. The armed forces are equipped with the most advanced weaponry, including 5 Airborne Warning and Control Systems (AWACS) aircraft, which were sold to Sa'udi Arabia by the US in 1981, over Israel's strenuous objections, as part of an $8.5 billion arms deal. In 2000 Sa'udi Arabia spent $18.3 billion, or 13% of GDP on defense. The US maintains air defense missiles and interceptors on a rotational basis.