Major General Mario F. Montero, Jr. enlisted in the Army in 1966 and received his commission through OCS in 1967 as a Transportation Officer. His overseas service included a tour in Vietnam and for Operation Just Cause in Panama.

He commanded HQ Company, 5th Transportation Battalion, B Co. 503rd Supply and Transport Battalion, 29th Transportation Battalion, Division Support Command, 25th Infantry Division, 1st Corps Support Command, and Military Traffic Management Command. Other key assignments include Chief, Mobilization and Movement Control Branch, U.S. Army Personnel Command; Assistant Commandant, U.S. Army Transportation School; and Assistant Deputy Chief of Staff for Logistics, U.S. Army. He retired in 2000, having served 34 years.

His decorations and badges include: Distinguished Service Medal, Defense Distinguished Service Medal, Legion of Merit, Defense Meritorious Service Medal, Meritorious Service Medal (w/2OLC), Joint Service Achievement Medal, Army Achievement Medal, Senior Parachutist Badge, Air Assault Badge, Ranger Tab, and Army Staff Identification Badge.