Shoulder patch for US Military Assistance Command in Vietnam. The United States Military Assistance Command, Vietnam (MACV) was established on Feb. 8, 1962, as a unified command subordinate to the commander-in-chief, Pacific. MACV has the mission of assisting the Republic of Vietnam Armed Forces to maintain internal security against subversion and insurgency and to resist external aggression. With headquarters in Saigon, MACV controls all of the United States Armed Forces in Vietnam. MACV is involved in two basic activities. Its forces constantly seek to engage the enemy in combat on the ground and territorial waters of the Republic of Vietnam, to provide assistance to the constitutional government of Vietnam in building a free society capable of defending itself.