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The Cambodia Campaign

The Reality Of Combat Signal Operations

As a young Second Lieutenant at my first permanent duty station in Vietnam, among the assignments I was given was to periodically command, usually as Officer Of The Day, a platoon of Infantry soldiers that provided perimeter defense for our signal site. Part of a Company reassigned after 7 months of front line search and destroy duty along the Cambodian border, these tough and seasoned 4th ID boys provided site defense for us Signaleers, while at the same time resting up from their own recent past of nearly constant, daily jungle combat. For them, providing defense for our signal site, sitting up high at 7,800 feet on top of Nui Lang Bien (Central Highlands) was like a holiday, compared to what they had been doing for the past half dozen months or so.

Nui Lang Bien, Dalat Area, 1969I enjoyed the hell out of working with them, as they provided me not only with relief from the boredom of watching my microwave communication gear hum along sweetly every day without failure, but also because they gave me a chance to pick up practical experience in everything from sighting in mortars to identifying combatants in the field.

Which brings us to the issue of this article: numerous times while I was in charge of the infantry boys they would call me to one of the guard towers that circled our signal site to point out NVA troop movement in the fields far below us. From up at our altitude we could easily see out 30 or more miles, watching all that took place around us. Sitting in their guard towers they often saw single files of NVA troops moving from west to east, coming from the Cambodian border some 40 miles away, and going God knows where. Their question to me was always the same, and the conversation usually ran along these lines: Sir, see that single file of 6 men down there in the valley? The ones moving through the hills on the other side of the lake? Those are NVA regulars. They’re moving from the Ho Chi Men Trail to our west towards Dalat (to our east). From there they’ll probably regroup and move on to Cam Ranh or Phan Rang. Do you want us to call in some Arty on them?

While I did, all too often the 4th ID Captain who ran our site and whose troops I was actually temporarily commanding thought that calling in fire on a small group of NVA marching through our area was the same as sending them a personal invitation to come back that night and visit us… generally in greater numbers, and generally around 0400 - 0430... more likely than not in the form of a serious attempt to breach our perimeter defenses and give us a little payback. Since we had suffered a few of these I tended to let him make the decisions on this matter... like, I had any say in the matter anyway, right?

Anyway, time and again he reminded me that he and his troops were on the signal site to provide defense for us, not offensive action against the VC or NVA. So, rather than approve my request to call in fire on what we saw, he merely directed me to wait until the NVA had exited our free fire zone and then report what I saw to HQ so that someone else further down the line could watch what they were up to.

To me it sounded screwy, but what the heck… I was a Signal Corps Officer, what did I know about how Infantry Captains go about making decisions as to who they will hit and who they will avoid. For all I knew he was under orders to do nothing more than make sure that we were safe in our little signal site in the sky, avoiding a direct engagement whenever he could.

Ho Chi Minh Trail - Near Tchepone PassEither way, the continued occurrence of these troop movement sightings made me wonder about the Ho Chi Minh Trail, and what was lying out there on the other side of the Cambodian border, only a few miles away from where I was sitting.

Today I know the answer to those questions. While I knew a bit about it back then, I didn't really know the details of what the Ho Chi Minh trail was or how important it was to the enemy. Back then I had never heard of the "Sihanouk Trial" or any of the other nuances of what that infiltration system was all about. Now, all these years later, I know what these things were about. I know what the Nape Pass was, as well as the Mu Gia Pass and even the importance of the Cambodian town of Tchepone. I also understand why North Vietnam set this system up, but what I don’t understand is why it took us until the mid-70s to invade Cambodia and try to put an end to this Olly Olly In Free sanctuary that we let our enemy have. For that matter, I don't understand  why we never invaded the North itself, to defeat the North Vietnamese in their own back yard?

Sure, I’ve heard all the excuses that have been trotted out over the past 40 years: that to do so would have broadened the war, invited retaliation from China, led to a nuclear war, violated UN resolutions, and on and on… but I mean, if you are going to fight a war, how about fighting to win, instead of just playing around in a delimited sand box that the enemy can leave for their own safety any time they get tired and need a break… but you have to stay in and take it?

To me it’s kind of like letting the Taliban run back into Pakistan when they need to rest and recoup. If the Taliban are in Pakistan, then why aren’t we there too? But then again, hey, I didn’t understand why my Infantry Captain never allowed me to call in Arty fire on the NVA we watched traversing our free fire zone, so why would I ever understand a decision to let the Taliban have a sanctuary in Pakistan or anywhere else for that matter?

Ho Chi Minh Trail - 1969At any rate, as all of this relates to us Signal guys, back in 1970 Nixon finally got fed up with the NVA using the Ho Chi Minh and Sihanouk trails as staging routes for incursions into South Vietnam and authorized what became known as the Cambodia Campaign (or Cambodia Incursion… depending on whether you were a hawk back then or a liberal). Centered around a series of short, spirited engagements, the Cambodia Campaign sent a bunch of RVN and US troops over the border into Cambodia to clean house, after which they were promptly removed (God forbid we should offend someone by actually staying there and occupying territory that our enemy was using as a staging and R&R area).

According to the history of the times, when Prince Norodom Sihanouk (leader of Cambodia) was deposed in March 1970 by a coup mounted by pro-American General Lon Nol, the U.S. felt it no longer had to worry about China entering the war. I guess, somehow, magically, the powers to be back in Washington decided that because Lon Nol was there we were in some way now able to cross over into Cambodian and do our best to shut down the Ho Chi Minh and Sihanouk trails… something we hadn’t been able to do prior to that without the world’s permission. Now though, now that Lon Nol was in charge, it was o.k. for us to go into Cambodia and do what we should have been doing for the past 16 years… albeit for only a month or so at a time before we had to get back on our side of the border, where one presumes the world felt we belonged.

Either way, the campaign was approved and its execution assigned to the 1st Air Cavalry Division. Along with RVN and ROK support, the 1st Air Cav would do the bulk of the fighting during the Cambodian Campaign, under the guise of something that was known as Operation SHOEMAKER.

Not surprisingly, the biggest test they met had nothing to do with their fighting skills, it had to do with their ability to communicate. After all, while we Signal boys had plenty of commo links running around South Vietnam we had no communication sites or links in Cambodia. For us, Cambodia was virgin territory.

Fortunately, the actual campaign was preceded by a short period of planning, and so in April 1970 the Signal Corps and the 1st Air Cav got down to some serious talk about how communication would be provided for one of the first elements of the campaign: an operation into what was called the “Fishhook,” an area along the Vietnamese-Cambodian border where the border line formed a, well… fishhook.

Part of War Zone C in the Binh Long and Tay Ninh Province area, II Field Force Headquarters was responsible for this area and wanted it cleared of the COSVN (Central Office of South Vietnam) known to use it as their own HQ area for attacks into what most of us called III Corps. Yet while time was allowed for planning, it wasn’t much. The division was ordered to be ready to commence operations and troop movements within 72 hours. And since COSVN was the target, and since they represented the highest command level responsible for activity in the South Vietnam base area, the orders were clear: neutralize and destroy the enemy. Period.

III Corps, Quon Loi - Cambodia CampaignNot surprisingly, with a name like Operation SHOEMAKER the task force involved fell under the command of Brigadier General Robert Shoemaker (technically, the operation was named after him, not the other way around… but you knew that, didn’t you). At the time General Shoemaker was the assistant division commander for all maneuver activities. Recognizing that for an over-the-border assault to flow smoothly he needed to reduce as much as possible the transport of both personnel and equipment, he located his task force HQ with the 3rd Brigade at Quon Loi. This he thought would help him get as much equipment as possible as far forward as possible, ready to support operations on the Cambodian side of the border, if needed.

Simple on paper, the plan was difficult to execute. One of the biggest problems centered around how the Signal Corps was going to get enough reliable communication in place to handle the rapidly increasing size of the task force.

Just as in our story posted on the November 2012 Home Page of the difficulty WWII Signaleers had in keeping up with the rapid advance of field forces as the front line moved forward towards Germany, here too in Vietnam the problem of how Signals could provide fast and dependable communication as the battle unfolded was crucial to its success. But in this case, unlike as in WWII where the problem was how to provide mobile communication at a time before it was either available or reliable, the problem here was how to stop all of the mobile radios that everyone was carrying from interfering with each other to the point that no one could communicate.

In the end, if the troops involved couldn’t communicate, then the operation would be in trouble. Fix the enemy they might be able to do, but if they couldn’t call in fire support they wouldn’t be able to wipe them out without a long, slow, ground based slog, swapping small arms fire until one side or the other withered and lost. Considering that more than enough fire power was available on our side to win this battle, falling back to a small arms engagement made no sense at all.

Quon Loi - Cambodian Campaign - 1970To be specific, the problem was that the communication gear everyone was using was alike, and since there were a ton of units involved in this battle it was likely that frequency interference would be high, perhaps to the point that no one would be able to communicate. Structurally, the force was composed of the 3d Brigade, 1st Cavalry Division; the 11th Armored Cavalry Regiment; the 3d ARVN Airborne Brigade; and all of the other standard support units from artillery to an entire assault helicopter company. Behind all of this the task force was reinforced by a mechanized infantry battalion from the 9th ID; a tank battalion from the 25th ID; another battalion from the 199th Light Infantry Brigade (the 5th Battalion, 12th Infantry); and two extra battalions from the 2d Brigade, 1st Cav. With all of these troops operating in a 30 by 30 square mile area, signal interference was sure to happen.

Operation SHOEMAKER kicked off on 1 May when the 3d Brigade leaped north across the Cambodian border. At nearly the same time the 11th Armored Cav Regiment struck to the north–northeast of the fishhook area while three battalions of the ARVN 3rd Airborne Brigade rode assault choppers into three separate target areas, one to the west of the ACR, and two to the south, down towards the Parrot’s Beak. The plan was that everyone would probe their area to locate the COSVN HQ and then move together in a large pincer movement to fix the enemy and cut off escape routes.

As more and more units deployed it soon became evident that back at Quon Loi communication was deteriorating to the point of becoming nearly impossible to establish. FM (frequency modulated) radio was the biggest problem, because most of the units, from the largest down to the smallest detachments and squads, used an FM radio as their Nui Ba Den - Vietnam 1970primary means of contact. With so many of them out there what people found was that when they hit their transmit keys either their signals were being squashed by all of the other signals, or they were squelching out someone else’s transmission. All across the frequency spectrum interference was occurring.

Adding to the problem was the difficulty of figuring out what frequencies people could switch to to avoid congestion. Because of Charlie’s tendency to listen in on our communication, units had adopted the habit of assigning their own frequencies to their own people, squads, platoons, companies, and more, requiring that these frequencies be kept top secret and not disclosed to anyone outside of the unit, even friendlies. Because of this, throughout the Army it was more likely than not that the frequency one unit assigned and used was being used by several other units. Since it hardly ever occurred that so many units from so many different brigades, regiments and divisions would operate in such a closed area, it was rare for interference to occur. During Operation SHOEMAKER however that wasn’t the case. Everyone was talking on top of everyone else.

An example of the size of the problem can be seen by looking at the congestion occurring between the 9th Infantry Division, 25th Infantry Division, and 199th Light Infantry Brigade. With everyone using the same equipment but assigning their own signal operation instructions, cipher key-lists, operation code material, and frequencies it was to be expected that congestion would occur. And it did. That is, it did until the Signal Corps stepped in to try to coordinate frequency assignments across units.

Nui Ba Ra - Vietnam 1970The antenna farm that had sprung up at Quon Loi showed how bad things were. At least a hundred FM radio nets were in operation within a half mile or so of the joint task force headquarters, with most of them using the same AB-216 tower. One of the written accounts of this battle claimed that “at one time nine VHF, one UHF, seven log periodic, and thirty-six 292 antennas could be counted on one tower belonging to the 3d Brigade. This number was in addition to antennas mounted on the towers of the 11th Armored Cavalry Regiment and 595th Signal Company (36th Signal Battalion) which were located less than three quarters of a mile away.”

Recognizing the mess that was occurring, the Signalmen supporting the Operation jumped to the task of straightening out the congestion by adjusting each FM receiver/transmitter to achieve peak power output. To help further assure that communication got through they also implemented field expedient airborne-to-ground relays on Nui Ba Den (also known as Black Virgin Mountain) and Nui Ba Ra, a couple of local mountains. By repeatedly going through the sequence of adjusting for maximum power output, fine tuning and switching each frequency where needed, reconfiguring and relocating antennas so that interference was minimized, and checking and rechecking the avionics equipment, everyone was soon able to communicate across the FM bands.[1]

Supplementing this an effort got underway to install a VHF (Very High Frequency) radio relay between Quon Loi and what was then called Camp Gorvad (located at a combination fire base and support airstrip near Phuoc Vinh). The link was based around a four-channel AN/GRC-163 system. This link held things together until after the operation was launched. At that time it became clear that even more circuits were needed, so  a new set of multi-channel communications was set up by the 36th Signal Battalion (Area) that provided communication systems for the II Field Force.

Phuoc Vinh, Vietnam - 1970While this was going on the 3rd Brigade provided telephone service via an SB-86 switchboard. Not surprisingly, even though the board had been expanded to handle 90 circuits it didn’t take long for it to be overloaded. By the third day of operations the Signalmen were forced to establish a separate switchboard geared to the requirements of the task force. This task fell to the personnel from the 13th Signal Battalion. So fast were communication needs evolving that Lieutenant Colonel Norman E. Archibald, talking about the battle years later, said, "To put it bluntly-it was a hand to mouth operation. We always kept our fingers crossed hoping that nothing would happen to the division wire system while we diverted personnel and material assets to the nodal head at Quon Loi."

All in all, keeping up with the evolving needs of the ground pounders and their helicopter buddies in the sky proved to be a real horse race. As more and more units were assigned to the task force it became harder and harder to find frequency assignments to meet the individual communication needs of each unit. The same was true for wire based communication systems. The problem there though was laying enough cable and wire to broaden the number of circuits available as fast as new units were being assigned. By day 5 of the Campaign the task force was the size of nearly 2 Divisions. When it became obvious that force strength was growing as fast as it was, command and control over the entire Operation was re-assigned back to the 1st Air Cav Division, at Phuoc Vinh. At the same time, the COSVN enemy having been found, the operation was refocused to the north and northwest of the area just inside the Cambodian border, versus the west and southwest thrust that the assault had originally begun with.[2]

Vietnam Air Assault - 1970By the 13th of May the 1st Cavalry Division had shifted its 3rd Brigade’s forces from the southern Fishhook area to an area further north, northwest of Bu Dop. In classic fashion as only existed during the Vietnam War they did this via a full-on helicopter supported air assault. The spectacle was something to see; something every soldier who served in Vietnam and ever saw or participated in one would never forget. The sight of an air assault, with so many choppers holding so much fire power, so many soldiers moving to engage the enemy, raised the hair on the back of your neck. America was advancing and nothing was going to stop it.

To make sure the VC and NVA did not backfill into the south and south-western portion of the Fishhook that had been emptied when the 1st Air Cav relocated, the U.S. 25th Infantry Division was moved into the space. Alongside of it the Vietnamese Airborne Division took up positions in the southern part of the Fishhook.

To keep COSVN troops from exiting the area targeted by the attack mounted by the 1st Air Cav the 1st Brigade and the 11th Armored Cavalry Regiment held their earlier positions in the northern Fishhook, in an area adjacent to what was known as the "Flatiron."

This tactical positioning was kept in place for 6 more days, when between the 19th and 20th of May the 1st Brigade, along with two battalions, were relocated again to the town of O Rang, Cambodia, just north of an area in Vietnam called Bu Gia Map (now part of a National Park; see map above right).

In the area where the COSVN had been located there were now eleven battalions, three armored cavalry squadrons, and the 1st Brigade Tactical Command Post, located at Fire Support Base DAVID, about 3 clicks northwest of the airfield at O Rang… right smack there in Cambodia. Finally, America’s Army was in Cambodia taking it to the enemy, instead of sitting back and waiting for the enemy to come to it.

Those familiar with the topography of Cambodia in this region know well that unlike the flat plains surrounding the Saigon area this area is and was full of both rolling hills and rugged mountains. Tactically this posed another challenge for the Signal boys: how to get communication up and running between O Rang, in Cambodia, and Division HQ, about 140 kilometers away. With lots of mountains and no previous recon having taken place, setting up reliable communication links was going to take some work. Adding to this was the question of whether troops would continue to use Fire Support Base DAVID or move on to yet another location. After all of the effort to set up this FSB, there were now concerns that the enemy’s forces had quickly fled the area and were no longer in the vicinity. If that was the case, then the force would need to move on as quickly as it arrived.

Fortunately, when the 1st Brigade assaulted O Rang on May 20, 1970, along with their guns they brought along personnel from the 13th Signal Battalion. And the Signal boys brought with them an AN/GRC-163 four-channel radio, two 1.5-kilowatt generators and several sets of fresh batteries. It took a while to get what they had up and running, but about 4 hours after touchdown communications was finally established when the Signal guys realized that, from their elevation of 3,000 feet at O Rang, they could reach a relay transmitter/receiver that they sent up and set up on nearby Nui Ba Ra. From there the VHF channels involved could be rerouted back to Phuoc Vinh.[3]

But their work wasn’t done. Once the link from FSB DAVID back to Phuoc Vinh was in place, the 13th Signal Battalion hung around in Cambodia, continuing to provide backup and support to the signal platoon that normally supported the 1st Brigade. If something was needed and the 1st Brigade’s Signal platoon didn’t have it, the 13th jumped in, sourced it, and had it delivered to O Rang by the next chopper available.

Silver StarIt took the NVA a few weeks to sort things out and figure out where the U.S. forces were, and who they could take a shot at. At about 0430 on the morning of 14 June the NVA finally struck Fire Support Base DAVID. Intent on breaching the perimeter they assaulted from three sides. Not surprisingly, they were driven off, albeit only after a very nasty fight. In the process the Brigade’s Signal Officer and several Signaleers were severely injured. As important, much of the equipment was destroyed. Even so, Acting Sergeant Goldsworthy, in charge of the VHF system and a Signaleer in the true sense of the word not only maintained communications throughout the firefight but earned a Silver Star for gallantry in the process.

Overall the Cambodia Campaign took place over a 60-day period from 1 May to 29 June. It was supported by a 75 day South Vietnamese incursion into Cambodia. The combined tactical and operational impact was remarkable. In the span of time involved the assault resulted in 11,562 enemy killed and the capture of an inestimable amount of materiel and information. So much material was captured that the NVA could have armed 54 battalions of 450 men each, with enough ammunition to sustain them in combat for a year, and enough rice to feed them for 6 full months.

When the campaign was over HQ MACV (Military Assistance Command Vietnam) estimated, "It would take the enemy a minimum of 9 months to reorganize his logistics and…up to 6 months to replace the men lost." Overall the Cambodia Campaign was inordinately successful. If it had a failing it was that it ended. That is, the effort to invade Cambodia and clear it of enemy should have continued until the enemy was defeated. Instead, pressure on the White House from the media, especially over the Kent State shootings, brought to the surface enough public outcry to force the President to set operational restrictions on the length of time we were all allowed to stay in Cambodia, and how far in we could go.

The question must be raised, how in God’s name can a country win a war with this kind of strategic quarterbacking going on by politicians more worried about what the media thinks than whether the boys in the field can do their job? We had the troops, we had the equipment, we had the transportation,  we had the signaling capability, and we had the need and gumption to invade Cambodia and roll up the NVA all the way back to the Mu Gia pass… where we could then have turned right and come down on Hanoi from the north, and ended that war on our terms.

Why weren't we allowed to? Hopefully, the next time America decides to go to war we’ll fight where the enemy is, not where the enemy wants us to be… the media and politicians be damned.

Phuoc Vinh - Award Ceremony




[1] Vietnam Studies, Division Level Communications, 1962-1973; Lieutenant General Charles R. Myer, DOA, Washington, D.C., 1982. - To return to your place in the text click here: Return to place in text

[2] During the Vietnam War a U. S. Army Division typically consisted of 17,000 to 21,000 soldiers commanded by a major general. Two Divisions generally composed a Corps with each Division consisting of four maneuver Brigades, an Aviation Brigade, an Engineer Brigade, and Division Artillery, along with a number of smaller specialized units. In the Cambodia Campaign the number of troops involved approached two Divisions in size, but were not assigned as such to a Corps. In 2007 Division Artillery was removed from most Division structures .  - To return to your place in the text click here: Return to place in text

[3] AN/GRC-163: A radio terminal set providing point-to-point infantry communications. Includes four voice and two teletypewriter circuits plus orderwire, VHF, FM. Major components include modified R-442 and RT-524. Total weight 231 Lbs; reference TM 11-5820-713-15 (click TM number at left to download a PDF version of  the original TM manual for the AN/GRC-163). - To return to your place in the text click here: Return to place in text

Additional Sources

Jeremiah S. Boenisch; The Cambodian Incursion: A Hard Line for Change, post graduate study white paper.

Various unattributed photos used in this article sourced from the My Vietnam Experience website.

Lieutenant General Charles R. Myer; Vietnam Studies, Division-Level Communications  1962-1973; Department Of The Army, Washington, D. C., 1982 


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This page originally posted 18 February 2013. It is a reprint of an article originally posted on the Home Page on 1 December 2012.

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