Period of conflict
For purposes of this subsection, the Vietnam conflict began February 28, 1961 , and ends on the date designated by the President by Executive order as the date of the termination of combatant activities in Vietnam. For purposes of this subsection, an individual is in a missing status as a result of the Vietnam conflict if immediately before such status began he was performing service in Vietnam or was performing service in Southeast Asia in direct support of military operations in Vietnam.