The total strength of the armed forces in 2002 was 110,000 active personnel supported by 188,000 reserves. The army numbered 70,000 equipped with 275 main battle tanks and 110 light tanks. The navy of 25,000 included 4,000 marines, 1,000 Coast Guards, and 800 Naval aviators. The air force numbered 15,000, with 116 combat aircraft and 19 armed helicopters. The navy operated six submarines, one cruiser, four frigates, and ten smaller combatants. About 77,000 paramilitary troops comprise the national police force. The armed forces face opposition from the Maoist Sendero Luminoso and the Movimiento Revolucionario Tupac Amaru, each approximately 600 strong. Peru sent observers to peacekeeping efforts in two African regions. In 2001 defense expenditures amounted to $1 billion or1.8% of GDP.