In 2002 Singapore's armed forces numbered 60,500 active personnel supported by around 312,5000 reservists. The army had an estimated 50,000 personnel, including 3 combined arms divisions; the navy had 4,500 personnel and a fleet of 24 ships, including six corvettes and six missile craft, and two Challenger submarines. The air force totaled 6,000 personnel operating 126 combat aircraft and 28 armed helicopters. Paramilitary forces numbered an estimated 96,300 including a police force and a civil defense force. Singapore participated in three international peacekeeping operations, and had troops abroad in five different regions. The 2001–02 defense budget was $4.5 billion or approximately 4.9% of GDP.