Combat Operations in Late 1966: I CTZ and the DMZ
In northern I Corps, Operation HASTINGS had largely driven the NVA 324B and 341st Divisions back across the DMZ with heavy losses, but the enemy’s future intentions remained cloudy. Immediately upon termination of HASTINGS, III MAF initiated Operation PRAIRIE in order to detect and forestall renewed infiltration. The Marines felt the enemy was avoiding contact but COMUSMACV instead worried what "might occur if the two NVA divisions did, in fact, elect to move into the Quang Tri area.” In response to this threat, real or imagined, on 24 September the 6994th established a temporary presence at Da Nang, including the entire DRILL PRESS contingent. An average of four ARDF aircraft and their crews also rotated through from Tan Son Nhut. On 16 October DRILL PRESS moved to the airbase at Hue/Phu Bai to ensure even closer contact with the 8th RRFS, which provided technical support for the mission. The outstanding work of the DRILL PRESS crews elicited a congratulatory message from the Director, National Security Agency.
In October-November, the 360th flew 97 sorties into the STEEL TIGER and TIGER HOUND areas of Laos, looking for enemy units which might suddenly attack across or just below the DMZ1. Although only 26 fixes were specifically reported in these two areas, such “across the fence” missions were a harbinger of things to come. On 7 December the 360th ceased operations from Da Nang, handing off mission responsibility in that area to the 361st and Det. 1 of the 6994th. There was no invasion of Quang Tri Province, but there was much bloody fighting nonetheless. Some of the worst centered around the stark outcropping known as The Rockpile, destined soon enough to be the scene of other fierce battles.
In all, PHYLISS ANN provided 278 fixes in support of PRAIRIE, including a record 138 in November. The Marines claimed more than 1,000 enemy killed but lost over 200 of their own, with more than another thousand wounded. PRAIRIE would continue into 1967, and the area around the DMZ would remain a deadly battleground.
II CTZ: Battles from the Highlands to the Coast
Two Corps was the largest of the four CTZ, incorporating some 46% of the land mass of South Vietnam. Providing security against a large and aggressive communist presence in the populous "national priority areas" along the coast required a considerable portion of available allied forces, diminishing the ability to conduct offensive operations in the desolate border regions of the highlands. From the earliest days of U.S. involvement in Vietnam, two possible enemy thrusts most concerned American advisors and later COMUSMACV. One was a conventional attack across the DMZ, the specter against which the Marines stood guard in northern I Corps. The other was an attack out of Cambodia towards Pleiku and Kontum, then down Highway 19 to the coast, splitting South Vietnam in half. The Ia Drang campaign in the fall of 1965 and the ongoing PAUL REVERE operations begun in May, 1966, were spoiling attacks intended to thwart enemy plans along those lines.2
Throughout the summer, successive PAUL REVERE probes generated off-and-on contact with the enemy which, when it did occur, was often vicious. On several occasions, only timely and effective close air support by USAF FACs, fighter-bombers, and AC-47 “Spooky” gunships prevented outnumbered allied units from being overrun. By mid-October, intelligence indicated that the enemy was poised for a virtual replay of the initial phase of his 1965 plan: Hit hard at the Special Forces outposts west and southwest of Pleiku City then ambush the U.S. and ARVN forces coming to their relief. Six regiments of the 1st and 10th NVA Divisions, at least two of them not previously identified, were believed to already be in South Vietnam or waiting in base areas just over the border in Cambodia. Again, MACV acted to spoil the projected NVA offensive, kicking off Operation PAUL REVERE IV on 18 October. U.S. Units were shifted about as events unfolded, but the main U.S. force consisted of a brigade each from the 4th and 25th Infantry Divisions and an airmobile brigade from the 1st Cavalry Division.
Action was sporadic, but once again close air support frequently proved to be the decisive factor. ARDF contributions to the PAUL REVERE operations are difficult to assess. Between mid-October and early December, EC-47 units fixed right at 100 targets in support of its four distinct phases. ARC LIGHT strikes were abundant, and at least some of these must have been in response to intelligence based on ARDF. In the words of an army history written years later, PAUL REVERE “ended without certainty.” The enemy offensive had failed and his units had taken a severe pounding, more from B-52 strikes and artillery fire than from close combat. But his Cambodian sanctuaries remined inviolate, allowing him to rest, refit, and eventually resume the battle of attrition which had now become the central feature of the land war in Vietnam.
In the coastal lowlands, I FFV sought to minimize the quantity of the rice harvest ending up in the larders of the other two NVA divisions, the 3d and 5th, known to be in II CTZ. In the area to the south around Tuy Hoa, a series of minor operations early in the year, mostly involving 1/101st Airborne, had put the 5th NVA on the run. Operation SEWARD kept up the pressure in September-October, followed immediately by Operation GERONIMO. Only intermittent contact resulted, but eventually elements of the 5th Division’s 95th Regiment were encountered. The troopers of the 101st got the best of the fight, and on 24 November “American electronic intelligence”—most likely ARDF—indicated that the 95th had fled west. The airborne brigade gave up the chase and departed for the highlands to join PAUL REVERE.
In the northern end of II CTZ, previous operations had not only destroyed large amounts of enemy supplies but also yielded valuable intelligence which would soon be exploited. Beginning in September, the 1st Cav, along with the ROK Capital Division and ARVN units, went after elements of the NVA 3d Division in Operation THAYER I, and its offshoot, IRVING. Poor weather impacted not only ground operations but prevented effective assessment of the results of lavishly applied tactical air and ARC LIGHT strikes. In any case the enemy, particularly the 18th NVA Regiment, was hard hit. Unlike the PAUL REVERE campaign in the highlands, the number of reported fixes in support of THAYER/IRVING was minimal. On the other hand Operation BYRD, originally planned as a short-term, “economy of force” experiment involving a battalion or two of the 1st Cav in the Phan Thiet area, was the beneficiary of 51 fixes in the last three months of 1966. Iterations of THAYER would continue into 1967; BYRD would run for more than a year.
III Corps and COSVN
In III CTZ, MACV faced three main force enemy divisions subordinate to COSVN—Central Office, South Vietnam. In terms of military command structure, the “South Vietnam” in COSVN did not refer to all the territory south of the DMZ (i.e., the Republic of Vietnam) but was geographically more akin to the Cochin China of colonial days, encompassing most of III and IV CTZ and the southern portion of II CTZ.3 In the northwest corner of III Corps was the communist War Zone C, within which—and across the border into Cambodia—dwelt COSVN headquarters and the 9th VC Division. To the east was War Zone D and the recently formed 7th NVA Division. Southeast of Saigon, the VC 5th Division remained under the watchful eyes—and SIGINT ears—of the 1st Australian Task Force and nearby U.S. units.
In mid-October, a brigade of the 1st Infantry Division opened Operation SHENANDOA, hoping to bait the VC into occupying ambush sites which, once the battle started, would be blasted by pre-sited U.S. artillery and on-call airstrikes. The enemy at first refused to bite but on the 28th, “exclusively on the basis of intelligence provided by ARDF,” two battalions air assaulted into the suspected enemy location. Contact was made with platoon-size enemy unit, while “heavy volumes of artillery fire” and 68 tactical air sorties raked the area. The commanding general, 1st Infantry Division, afterwards passed along his compliments “for a job well done”, adding that “We need your continued support.” A follow-up search revealed a base camp with more than 200 bunkers, along with 74 enemy bodies. But the majority of the enemy force had slipped through the trap.
Meanwhile, COSVN was planning a renewed offensive. The 9th VC Division, hit hard by earlier allied operations but now rested and reequipped, was ordered to "destroy a 'vital' element of the enemy,” in this case the hastily organized 196th Light Infantry Brigade, fresh off the boat from the U.S.
The 196th, unaware of the enemy plans, initiated Operation ATTLEBORO on 14 September. The discovery of a large cache of rice led to further exploration and the addition of more troops to join the hunt. On 1 November, hints of the enemy’s plans were revealed. The brigade turned towards the provincial town of Dau Tieng, now intent on finding and destroying the supply caches upon which the enemy attack depended. From there, things went downhill rapidly. The VC turned on the green U.S. troops with a vengeance, launching “human wave” attacks that very nearly overran several American positions. When the enemy finally broke contact, action escalated as two brigades from the Big Red One were sent to catch the fleeing VC before they could cross into Cambodia. One prong of the American attack headed north towards the “fishhook” area, hard by the Cambodian border, where “electronic intelligence reports”, doubtless ARDF, had located sections of COSVN. ATTLEBORO eventually involved 18 U.S. and 3 ARVN infantry battalions, with commensurate air and artillery support, including 225 B-52 sorties which churned up thousands of cubic yards of jungle with little verifiable results. The ground sweeps uncovered and seized or destroyed yet more supply caches but could not determine “what percentage of the enemy's existing supplies and bases in War Zone C had been lost or how quickly they could be replaced.” Neither COSVN nor the 9th VC Division were strangers to the EC-47 crews which had provided CTS for the 1st Division’s search and destroy operations for the past several months. Well over 200 fixes had been made in support of SHENANDOA/ATTLEBORO alone. The VC were battered but unbeaten, and COSVN remained as elusive as ever.
PHYLLIS ANN at Her Finest
On 21 November a large convoy, part of Operation ATLANTA, was ambushed along Highway One between Bien Hoa and Xuan Loc. The convoy was escorted by nine “Armored Cavalry Assault Vehicles” (ACAV) of the 11th Armored Cavalry Regiment.4 In the convoy was the regimental S-2 (Intelligence) officer. With less than ten minutes to spare and the lead vehicles less than 1,000 yards from the ambush site, the S-2 received an intelligence report—in fact an ARDF fix from a PHYLLIS ANN bird—locating an enemy unit ahead.
Word was quickly passed and as the convoy entered the ambush zone, the ACAVs opened fire into the roadside brush, momentarily upsetting the enemy’s plans. About half the convoy raced through the killing zone before a truck was stopped cold by a recoilless rifle round, blocking the road. A furious firefight ensued; a pair of ACAVs coming to the rescue were likewise disabled.
The surviving ACAV’s and the dismounted troops from the rear of the convoy, with hastily called-in fire support from helicopter gunships and USAF fighter-bombers, finally forced the enemy to cease firing and withdraw, leaving behind 30 bodies and several weapons. Seven Americans lay dead, another eight others were wounded. Two ACAVs were destroyed, along with four “deuce-and-a-half” trucks. It could’ve been much worse. In the words of an 11th ACR message: “This ARDF [fix] prevented a serious ambush for which the supported command is indebted.” 5
Six Successful Months
As the clock ticked down the last hours of 1966, the men of PHYLLIS ANN could look back on six months of solid achievement. Since the first mission on 6 June, over 1,000 ARDF sorties had been flown in which some 2,600 targets were fixed, almost a thousand of which were in close tactical support of no less than 38 named ground operations. Meanwhile, evidence began to suggest that the VC were aware that the Americans were utilizing airborne SIGINT collection platforms. Beginning in November, in an inventive attempt to disguise the ARDF mission, “Chiêu Hồi” safe-conduct passes were dropped; typically the countryside was littered with 50,000 of these per sortie. Somewhere along the line, most if not all EC-47s had a leaflet chute installed in place of the rearmost right-side window, but for cost or other reasons the psychological warfare cover was eventually abandoned.
To this point, there had been no serious accidents or injury to PHYLLIS ANN personnel or aircraft due to enemy action. But as a reminder that there was no place in South Vietnam that the enemy could not reach, in the early hours of 4 December a combined VC sapper penetration/mortar attack on Tan Son Nhut killed three USAF airmen and wounded 15 others. Five EC-47s were among the 20 aircraft hit, one of which (42-92166) incurred major damage requiring approximately 600 man hours (and $2,680) to repair and knocking it out of action for 18 days. The New Year would not get easier.
NOTE: Click on images above for larger view.
1. See previous article, Phyllis Ann Settles In. In April, 1965, interdiction of the enemy’s infiltration system in the Laotian panhandle was separated from BARREL ROLL into a separate operation named STEEL TIGER. TIGER HOUND was a further subdivision taking in the areas in Laos immediately adjacent to the central highlands in the western areas of I and II CTZ. Click here for a map of these areas.
2. See previous article, The Point of No Return, paragraph heading "Into Battle."
3. The Military Regions further north reported directly to Hanoi.
4. The rolled up chain link fence on the lead ACAV in the photo was erected in night defensive positions. This fencing was effective in blocking RPG rounds.
5. Click here to view the 360th feedback report and the 11th ACR AAR concerning this incident.
Click here for sources referenced in this article.
Article by Joe Martin
21 March 2017