Paraguay's armed forces amounted to 18,600 active personnel supported by some 164,500 reservists. The army numbered 14,900 equipped with 12 main battle tanks. The navy of 2,000 included 900 marines and 100 naval aviators. The air force had 1,700 personnel with 28 combat aircraft and no armed helicopters. There was a paramilitary force of 14,800 in the special police service. Paraguay has compulsory military service of one year for all males 18 years of age. Expenditures of the Ministry of Defense were $125 million in 1998, or 1.4% of GDP.