U.S. advisers in the Vietnam War
- See also: Foreign internal defense
U.S. foreign policy often stops short of active combat intervention, but, as with U.S. advisers in the Vietnam War, may take increasingly active roles in supporting what is called the Host Nation (HN). Current doctrine assumes that the HN faces an internal or external threat, for which the response is foreign internal defense (FID). FID is different than general foreign military aid and training in the absence of specific threats. Both FID and general assistance, however, conceptually are part of U.S. grand strategy. In some situations, there may be clandestine assistance to a HN through the Central Intelligence Agency, and, in other situations, the assistance may be to opponents of the existing government under the doctrine of unconventional warfare).
Before the 1954 Geneva accords and the defeat of French power, there was U.S. involvement both in an observer role, and in assistance to its ally, France, in the form of Military Assistance Group, Indochina (MAAG-I). When France gave quasi-state recognition to Vietnam, the program transitioned to Military Assistance Advisory Group, Vietnam (MAAG-V). As with many involvements, that began at a headquarters level, but became much more complex as time went on and conflict intensified. The prospect of combat created a need for a different organization, Military Assistance Command, Vietnam (MAC-V), which absorbed MAAG-V as the headquarters for the advisory function.
Roles of advisers
Originally, advisers were just that: they gave advice to Army of the Republic of Viet Nam (ARVN) personnel. Increasingly, with varying success, the advisers controlled U.S. fire support (air and artillery), combat support (primarily intelligence and communications) and combat service support (logistics and other rear area services). When there were multiple, confused chains of command, the results could be disastrous, as at the Battle of Ap Bac. There could also be effective cooperation, including coordination between ARVN and U.S. military combat operations, as at the Battle of the Ia Drang.
Anthony Zinni, who would rise to four-star general, speaks of both teaching and learning with Vietnamese Marines.  Another U.S. officer who would attain the highest rank, had the highest respect for the ARVN Airborne Brigade. 
The most successful U.S. advisers became close to their counterparts, even sometimes defying U.S. commanders, and tried to understand both general and military Vietnamese culture. Special bonds developed there, and, above all, when Americans would risk their lives for their counterparts; there is an iconic picture of then-Schwarzkopf carrying wounded ARVN troops out of a minefield. Other U.S talented U.S. advisers, such as John Paul Vann], often had contempt for the Vietnamese officer corps, and this hurt relatioships. In yet other cases, especially with United States Army Special Forces, local Vietnamese, especially of minority groups, preferred the U.S. personnel and even tried to get them to join in revolts against the Government of Vietnam.
- Clancy, Tom; Tony Zinni & Tony Koltz (2004), Battle Ready, Putnam, pp. 32-34
- Schwarzkopf, H Norman, Jr. (1992), It Doesn't Take a Hero, Bantam, pp. 122-123