He was commissioned in the Ensign 1915 Program in 1966. His early assignments included serving as the Senior Medical Officer aboard the amphibious assault ship USS NEW ORLEANS, and as a General Medical Officer at Marine Corps Recruit Depot, San Diego, California. During a subsequent assignment to Naval Hospital Camp Pendleton in California, he held a progression of assignments such as Staff Surgeon; Chairman, Department of Surgery; and finally, Director of Surgical Services.

Rear Admiral (Lower Half) Johnson was next assigned to Naval Hospital, San Diego, as Assistant Chairman, Department of Surgery. In 1989, he was transferred to Washington, DC, where he held the position of Deputy Chief of the Medical Corps. Upon transfer to San Diego in July 1991, he was assigned as Medical Director at Naval Hospital San Diego, and was subsequently named Deputy Commander, a position which he held until February 1994. During his next assignment, he assumed command of Fleet Hospital SIX, which deployed on a United Nations mission in Croatia. In October 1994, he became the Commanding Officer of Naval Hospital, Bremerton, Washington, where he served until August 1997. He was then selected as the Principal Director for Clinical and Program Policy in the Office of the Assistant Secretary of Defense for Health Affairs. In August 1998, Rear Admiral (Lower Half) Johnson was reassigned as Medical Officer of the Marine Corps, Headquarters, U. S. Marine Corps, Washington, D.C. He supports the missio

n of Navy Medicine as the Medical Officer for the Marine Corps by maintaining liaison between the Navy Surgeon General and the Commandant of the Marine Corps. He advises the Commandant of the Marine Corps headquarters staff agencies on all matters affecting medical and dental support for the Marine Corps.

Rear Admiral (Lower Half) Johnson earned certificates from the American Board of Surgery and the American Board of Medical Management. He is an Assistant Clinical Professor of Surgery at the Uniformed Services University of Health Sciences. His affiliation with civilian medical organizations include his status as a Fellow of the American College of Surgeons, and he is a member of the American Medical Association, National Medical Association, American College of Physician Executives, Association of Military Surgeons of the United States, and Society of Medical Consultants to the Armed Forces.

His military decorations include the Defense Superior Service Medal, Legion of Merit, Meritorious Service Medal, Navy and Marine Corps Commendation Medal, Joint Meritorious Unit Citation, Navy Meritorious Unit Citation, National Defense Medal, Vietnam Service Medal, Armed Forces Service Medal, Humanitarian Service Medal, Philippine Presidential Unit Citation, United Nations Medal (Yugoslavia), NATO Medal, and the Vietnam Campaign Medal.