From December 1967 to July 1969, Stewart served at
Fort Devens, Massachusetts, where his assignments included training officer (December 1967 to February 1968), maintenance officer (February to April 1968), assistant family housing officer (April to May 1968), and a second posting as maintenance officer (May 1968 to July 1969). He was promoted to
first lieutenant in December 1968. Stewart served in
South Vietnam during the
Vietnam War, and his postings included Section Commander, 121st Aviation Company (July to August 1969), Assistant Platoon Commander, 121st Aviation Company (August to October 1969), Platoon Commander, 121st Aviation Company (October to December 1969), Assistant Platoon Commander, 121st Aviation Company (December 1969 to February 1970), and Platoon Commander, 162nd Aviation Company (February to August 1970). After returning to the United States, he was posted to
Fort Stewart, Georgia, where he served as executive officer of Company D, 2nd Aircraft Maintenance Battalion from August to December 1970. From December 1970 to January 1971, he was plans officer on the staff of
Third United States Army's Aircraft Maintenance Brigade. He was the brigade's assistant plans officer from January to July 1971. From July 1971 to January 1972, he completed his regular army service as the brigade's assistant operation and training officer. ==Continued career==