Interpolations of the United Nations estimate of the country's 1973 population indicate that there were about 2.3 million males in the fifteen- to forty-nine-year age-group, which Bulgarian authorities consider military age. There were also about 70,000 in the annual groups that were reaching the draft age of nineteen each year. Those conscripted serve two- or three-year duty tours. The basic ground force tour is two years; that of special units and air and naval forces is three years. Approximately 70 percent of the military age groups, or 1.6 million males, are considered physically and otherwise fit for military duty. Any number of them could be called up in the event of an emergency requiring total mobilization, but it is likely that many of the group would be occupying positions having higher priority than basic military duty. A somewhat larger proportion, or about 75 percent, of the nineteen-year-olds are in satisfactory physical condition. Most of them are drafted; a turnover of one-third of the 150,000-man regular armed forces each year would require nearly all of the group. Because there is very little room for flexibility, a young man's education is interrupted unless he was actually enrolled in a university or college before he reached the age of eighteen. In this case he continues his education but serves his military obligation upon completion of his education. Occupational deferments were eliminated by law in 1970, and other deferments are given infrequently and reluctantly. Young men unfit for military duty or for work in the Construction Troops, but who are fit to earn a living in some other work, pay a military tax (see ch. 15). Those who have had military service and who have not reached the age of fifty are considered reserves. Officers remain in the reserve until the age of sixty. Various factors--primarily occupational situations, physical condition, and lack of reserve training--operate to erode this force, and those considered useful, or trained, reserves constitute one-half or less of the group. Most of the some 250,000 men released in the latest five-year period, however, are available, physically fit, and familiar with the weapons and equipment in use by the armed forces. Training In common with its Warsaw Pact allies, Bulgaria uses equipment that is produced or designed in the Soviet Union or that is compatible with Soviet designs. The training program is patterned after that of the Soviet army because the Soviet equipment dictates the training required to maintain and operate it, and joint maneuvers participated in by any or all of the pact forces make it necessary to employ standard procedures and tactics.