In 2002 there were 49,580 active personnel in the armed forces, with reserves numbering 32,200. The army numbered 23,150 including 1,630 women. Equipment included 328 main battle tanks. The navy had 13,800 personnel including 3,100 marines. Its fleet included four submarines and 12 surface combatants. The naval aviation unit of 950 was equipped with ten combat aircraft and 21 armed helicopters. The air force of 8,850 personnel (including 975 women) operated 143 combat aircraft and 30 attack helicopters. The constabulary numbered 3,300. The US stationed about 550 troops in the Netherlands. The Netherlands maintained forces abroad in Germany, Iceland, and the Netherlands Antilles. The nation also participated in UN and peacekeeping missions in seven regions. Military expenditures were estimated at $6.5 billion in 2000–01, or 1.5% of GDP.