Geronimo: Strategy Lessons from History’s Periphery

On the surface, 4 December 1966, appears inconsequential. In the context of the 1960s, a decade rife with major milestones for humanity, 4 December 1966, exists on history’s periphery. Yet upon closer examination, this date is representative of what was until recently America’s longest war. Small events shape history, yet do so subtly. In that vein, Operation Geronimo I revealed both the effectiveness and limitations of combating low intensity warfare with highly mobile forces. Deeper still, Operation Geronimo I demonstrated that operational successes were not trustworthy indicators of progress towards victory during the Vietnam War.

Technically, two significant events occurred on 4 December 1966 during the Vietnam War. One involved an attack against the United States’s largest base in the Republic of Vietnam, and the other a U.S. Army effort to spread pacification. On the same day People’s Liberation Armed Forces (PLAF)—pejoratively called the Viet Cong—attacked American military assets at Saigon’s Tan Son Nhut airport, I Field Force Vietnam (IFFV) wrapped-up another operation further north in the Republic of Vietnam’s Phu Yen Province.[1] There, U.S. Army maneuver battalions attached to IFFV sought to secure the province’s rice production and annihilate nearby enemy main forces. As envisaged by IFFV, the use of airmobile infantry battalions would push the enemy away from the population via search and destroy, thereby rapidly advance pacification. To that end, from January 1966 until the end of that year, U.S. Army soldiers conducted over ten operations in Phu Yen.

On 4 December 1966, IFFV ended Operation Geronimo I. Devised by IFFV as a three phase operation, only Geronimo I produced results. Having begun on 31 October, Geronimo I called for bringing battle to the largely illusive People’s Army of Vietnam (PAVN) forces lurking just beyond the rice paddies of Phu Yen’s Tuy Hoa Valley. A deluge of rainfall severely limited the effectiveness of Geronimo II, while IFFV cancelled the third phase. Before Geronimo I, enemy main forces had largely survived IFFV’s previous operations in Phu Yen. If Operation Geronimo I could finally bring those remaining enemy forces to a Waterloo-like battle, IFFV would significantly further the safeguarding of the province’s rice harvest and long-term stability under the Saigon government, a process that began early in the year with Operation Jefferson. U.S. Army participants in the operation included the 1st Brigade, 101st Airborne Division and the 4th Infantry Division.

The climax of Geronimo I transpired when U.S. forces made contact with the 95th PAVN Regiment. Between the end of October until 8 November, elements of the 1st Brigade, 101st Airborne Division exploited intelligence—gathered during previous operations—of PAVN movement in the remote mountainous areas of western Phu Yen. These American troops made contact with a PAVN force of an estimated one-hundred soldiers.[2] Other IFFV assets, however, made a more crucial find. On 10 and 11 November, elements the 95th PAVN Regiment found itself surrounded in the Ky Lo Valley by the soldiers of the 4th Infantry Division. IFFV tasked these troops with the mission of “finding and destroying elements of the 95th NVA Regiment by conducting a deliberate search of all trails, streambeds and probable avenues of egress along the SONG KY LO River In northwest DONG XUAN District.”[3] During those two days, the Americans located a sprawling enemy base area, which included “a manufacturing site containing two forges and an extensive hospital-dispensary.”[4] Such physical evidence of enemy activity and infrastructure revealed the Ky Lo Valley as a noteworthy PAVN and PLAF staging area for Communist operations in the province.[5]

U.S. Army Colonel David Hackworth considered Operation Geronimo I an example of how to defeat the enemy in South Vietnam. He noted that Geronimo I produced a 10:1 kill ratio and “the very high weapons-to-body count ratio (143 weapons, individual and crew-served, to 149 enemy dead)” as proof of success. For Hackworth, the operation revealed that “we’d be able to fight the same protracted war of attrition the enemy was willing to fight, without paying the heavy, heavy price in American lives.”[6] Such a vision relied on the ability of American forces to out maneuver the enemy through the use of air mobility. However, Hackworth’s statement did not adequately address how the enemy would respond. In the case of Phu Yen, American and South Vietnamese gains were more temporary than long-term. Hackworth himself admitted, “The enemy just went to ground and waited until the coast was clear to return and rebuild.”[7] Pacification needed offensive operations by IFFV to simply stay ahead of PAVN and PLAF efforts to create their own liberated areas. Put another way, search and destroy advanced pacification only while offensive operations continued. This was a reality that could not happen considering the need for IFFV’s assets in other provinces to combat enemy activity similar to that in Phu Yen.

A U.S. Army newsreel on Operation Geronimo I exposed the uninformed to the pacification war underway in the hinterlands of South Vietnam. Viewers saw recordings of soldiers of the 101st Airborne Division scouring the Phu Yen countryside for signs of PAVN and PLAF activity. As crafted by the U.S. Army, and as seen by viewers themselves, search and destroy was pacification. The implicit rendering of conventional warfare as pacification used military victories to make the war in the Republic of Vietnam’s countryside appear winnable.

Operation Geronimo I is symbolic of IFFV’s operations of 1966. Geronimo I marked the last time a sizable American military force entered the remote Ky Lo Valley. An enemy base area existed in this valley and did so without prolonged interference by U.S. Army, ARVN, and ROKA units. Deemed a success because of high body count scores, the operation further weakened the remaining elements of the PAVN regiment operating in Phu Yen. Yet, most significantly, Operation Geronimo I did not remove PAVN from Phu Yen. Therefore, 1966 concluded with an enemy force capable of supporting the Hanoi’s war effort in the province. Those two reasons aside, what makes Operation Geronimo I worth discussing now is how that operation symbolized pacification during the Vietnam War.

The American and South Vietnamese war effort in general worked so long as the U.S. military assets continued offensive operations. Yet PLAF attacks, similar to the aforementioned one against Tan Son Nhut, became the means by which the PLAF undermined pacification. In turn, low intensity warfare proved the true measure by which to gauge the progress of the war in Vietnam. Indeed, low intensity warfare as conducted by the PLAF relied more on demonstrating the vulnerability of American and South Vietnamese military forces than battlefield victories. Doing so revealed that American and South Vietnamese pacification could not protect the people and livelihoods of those caught in the middle of war. Applications of such truths to current conflicts requires understanding Operation Geronimo I as the apogee of conventional warfare as pacification, and that the temporary gains associated with the operation means planners of future counterinsurgency operations must focus more on the symbolism than effecting a Waterloo.

Robert J. Thompson recently completed his Ph.D. in U.S. History at the University of Southern Mississippi. His dissertation is titled "More Sieve Than Shield: the U.S. Army and CORDS in the Pacification of Phu Yen Province, Republic of Vietnam, 1965-1972."

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Header Image: Members of a rifle platoon ready themselves in the field during the Vietnam War. (Charlie Haughey/The Atlantic)


[1] Roger P. Fox, Air Base Defense in the Republic of Vietnam 1961–1973 (Washington D.C.: Office of Air Force History, 1979), 38. Available at: <>

[2] 322d Military History Detachment, The First Brigade in the Republic of Vietnam July 1956-January 1968 (Tuscaloosa, AL: U.S. Army Reserve, Undated), 44.

[3] Operational Report Lessons Learned, Department of the Army, Headquarters 1st Brigade 4th Infantry Division, sub: Operational Report Lessons Learned for Quarterly Period Ending 31 January 1967,” p.10, DTIC. Available at: Emphasis in original.

[4] Ibid.

[5] Ibid.

[6]  Hackworth and Sherman, About Face: The Odyssey of an American Warrior (New York: Simon and Schuster, 1989), 566.

[7]  Ibid., 571.