The Swiss army is a well-trained citizen's militia, composed of three field army corps and one alpine field corps. In 2002 the active armed forces consisted of 3,500 officers, with the ability to mobilize 320,400 trained troops within 48 hours. The country has universal compulsory military service for males at age 19–20, followed by varied annual training requirements until age 42 (55 for officers), with exemption only for physical disability. Initial basic training of 15 weeks is followed by regular short training periods. The paramilitary consists of a civil defense force of 280,000 members. Equipment included 556 main battle tanks, and the Air Corps has 138 combat aircraft.
Swiss fighting men are world famous, and from the 16th to the 19th century some two million Swiss served as mercenaries in foreign armies. The modern Swiss citizen-soldier is trained only for territorial defense in prepared mountain positions, which is his only mission. A continuing legacy of Swiss mercenary service is the ceremonial Vatican Swiss Guard. Switzerland participates in seven international peacekeeping operations. Military spending was an estimated $2.5 billion in 2001, or 1.0% of GDP.