of residency training. The “Berry Plan” deferred doctors who were taking their residency, so that the Army would get the benefit of their advanced education. Eventually, GME became both a recruiting and a retention tool for the AMEDD, and board-certified specialists were attracted in steady numbers. Those MC officers who did not elect Option 1, or who were not needed immediately, were “deferred.” Some were allowed Option 3, to complete their residency training and then entered active duty as a fully trained specialist. Those who were deferred for only one year of residency were termed “partially trained specialists” and were usually given military assignments that allowed them to work within their specialty. Many residency programs would give a year’s credit toward completion of residency for their time in military service to physicians who served under Option 2. (This triple option program continued for 19 years until the US military draft ended in 1973.) During the Vietnam era, serious physician shortfalls were experienced by the Defense Department and it was at this time (1966) that osteopathic physicians, who had previously been excluded from active military service, were first admitted to the MC. To avoid reinstating another “doctor draft”, the US Congress took steps to encourage medical students to enter the military as physicians. Completing this trend, medical school training has been provided for military students since the Uniformed Services University of the Health Sciences (USUHS) was established in 1972, graduating its first class in 1980. USUHS is the United States' center for military medical education. Its primary mission is to prepare its graduates for service in the medical corps of all the uniformed services of the country. Eventually, USUHS graduates made up about 25% of all doctors in the military. (Now it graduates about 164 physicians each year; around 90% of all USUHS graduates remain on active duty until reaching retirement eligibility.) By the mid-1990s, the strength of the Army's MC had risen to about 5,400 active duty officers, but cutbacks soon ensued. 21st century As of mid-2008, the number of active duty doctors serving in the MC nearly met the requirement of 4,448 authorized positions. Primary care specialties represented the greatest shortfall in endstrength numbers. Career management As with all Army officers, the military occupational specialty (MOS) classification system provides the MC officer with his/her officer branch, area of concentration (AOC), branch skill code (degree of proficiency), special qualifications identifiers