The last Vietnam veteran to be an active-duty Rhode Island National Guardsman has retired, more than 40 years since he first enlisted. Captain Richard Gaudet retired Saturday following a ceremony at the Benefit Street Armory in Providence. Gaudet enlisted in the US Army in 1971 at age 17. During the war he was stationed in Thailand and made repeated trips into Vietnam as part of an aviation support unit. Gaudet then joined the Army Reserve and completed officer candidate school with the Rhode Island National Guard. He reenlisted following the Sept. 11, 2001, attacks. Gaudet is a Providence native who now lives in Coventry.