Clark originally joined the Navy during the Vietnam War (as John Terence Kelly) and became a Navy SEAL who participated in several special operations, one of which was the rescue of a naval aviator shot down over North Vietnam. The aviator was the son of Admiral Dutch Maxwell and his rescue earned Kelly a promotion to Chief Boatswain's Mate. After his first tour of duty, Kelly left the Navy but was later re-hired by the Central Intelligence Agency's (CIA) Special Activities Division (Special Operations Group) for another mission in Vietnam; a rescue operation on a secret POW camp. At the same time, Kelly was carrying out his own war at home against a drug ring that killed his girlfriend, Pamela Madden. While he succeeded in taking it down, the Baltimore Police Department (including Emmet Ryan, Jack Ryan's father) eventually identifies him as the man who murdered the drug dealers. In response, Kelly faked his own death (with the help of the CIA, which falsifies the identity of his fingerprints in his Navy personnel file) and goes to work for the CIA full-time, under the pseudonym "John Clark". (See "Without Remorse") His middle name appears variously with one and two 'R's, and the name "John Terrence Clark" appears in the novel "Clear and Present Danger".