Kuwait's armed forces totaled 15,500 volunteers in 2002. The army had 11,000 personnel equipped with 368 main battle tanks. The air force numbered 2,500 and had 81 combat aircraft. The navy had 2,000 personnel and 16 craft. There is a 6,600-member National Guard. The UN provides troops and observers in Kuwait. The US maintains a military presence with 7,388 troops stationed in Kuwait. Estimated defense expenditures in 2001 were $1.9 billion or 5.5% of GDP.