Thomas John Hall "Trap" Trapnell was a United States Army lieutenant general. He was a career officer who served in World War II and the Korean War. Trapnell survived the Bataan Death March and the sinking of two transportation ships during World War II, put down a rebellion of prisoners of war in the Korean War, was the top US advisor to the French during the French Indochina War, and advised against US involvement in Vietnam. He rose to the rank of three-star general before his military retirement and, at the time of his death, was the oldest living member of the Philippine Scouts.

A Military Assistance Advisory Group (MAAG) is a designation for a group of United States military advisors sent to other countries to assist in the training of conventional armed forces and facilitate military aid. Although numerous MAAGs operated around the world throughout the 1940s–1970s, including in Yugoslavia after 1951, the most famous MAAGs were those active in Southeast Asia before and during the Vietnam War.