The President of the United States of America, in the name of Congress, takes pleasure in presenting the Medal of Honor to Captain & Aide-de-Camp Martin Thomas McMahon, United States Army, for extraordinary heroism on 30 June 1862, while serving with U.S. Volunteers, in action at White Oak Swamp, Virginia. Under fire of the enemy, Captain McMahon successfully destroyed a valuable train that had been abandoned and prevented it from falling into the hands of the enemy.