The Military Advisory Command-Vietnam-Studies and Observations Group, more commonly and simply called S.O.G., was a covert operations faction during the Vietnam War, the zombie apocalypse, and the Rebirth era. The S.O.G. was founded after the Central Intelligence Agency handed over control of certain territory in Vietnam. The purpose of S.O.G. was to combat the enemy, secure intelligence, and advise the regular Army and Marine Corps on missions. However, after the zombie incidents in multiple countries, the S.O.G. became a zombie fighting group as well as remaining a covert operations group. The Special Activities Division often recruited members of the S.O.G. to preform operations. The S.O.G. was primarily comprised of Marines and Army soldiers.