The Defense Distinguished Service Medal. Illustration by Virginia Reyes of the Air Force News Agency. This image is 4x6 inches @200 ppi. The Defense Distinguished Service Medal has been in effect since July 9, 1970. It is normally awarded to the most senior officers whose performance of duties over a sustained period of time are exceptional in nature and directly impact national security or defense at the highest levels. It is the highest peacetime Defense award and is only awarded by the Secretary of Defense.