Charles entered the Air Force in May 1968. After receiving his medical degree, he completed his internship and residency in obstetrics and gynecology at Keesler Medical Center. He is board certified in OB/GYN and is a diplomat of both the American Board of Obstetrics and Gynecology and the American College of Healthcare Executives. From 1996 to 1999 he served as the 16th Surgeon General of the Air Force, and retired in 1999 as an Air Force Lieutenant General. His father, by the same name, was also a medical officer who retired as an Air Force Major General.