In 2002, the armed forces totaled approximately 370,000 with reserves numbering 1,657,500. The army had 240,000 members including military police. Equipment included more than 900 main battle tanks. The navy numbered 62,000, including 30,000 marines, and operated four submarines and 32 principal surface combatants. The navy also had a naval aviation wing equipped with 32 combat aircraft and 20 armed helicopters. The air force had personnel numbering 68,000 operating 479 combat aircraft. Paramilitary included security groups of 25,000, including a National Police Administration, a Bureau of Investigation, Military Police and Coast Guard. Taiwan spent $8.04 billion on defense in 2001, or 2.8% of gross domestic product.