Story 78 - COMSEC in the Task Force

By Denis Hare OAM BEM

Denis 'Rabbit' Hare

“Without intelligence, one is vulnerable; without security, one is defenceless” 1

Military Security Terms

Communication Security (COMSEC) is the act of listening to, copying, or recording transmissions of one's own official telecommunications to provide material for analysis in order to determine the degree of security being provided to those transmissions. COMSEC monitoring by its nature is very selective and cannot monitor all communications all the time.  Furthermore, COMSEC uncovers lapses only after they have occurred 2.

COMSEC monitoring was conducted by the 1st Australian Task Force (1ATF) starting in early 1967 using a small team from Force Signals 3, under the direction of the Officer Commanding (OC), of the Task Force Signal Squadron 4.    The principles for communication security within the 1ATF was stated in the 104 Sig Sqn Standing Orders, Unit Security Instructions to be as per Allied Communications Publication ACP 125 Communications Instructions and Radio Telephone Procedures 5.

Signals Intelligence (SIGINT) is information gained by the collection and analysis of the electronic signals and communications of a given target.  SIGINT monitoring of enemy communications was the task of 547 Signal Troop (547 Sig Tp) within 1ATF.  The Troop was under operational control of the United States Army Security Agency’s 509th Radio Research Group and was assigned to the 303rd Radio Research Battalion.  See the Pronto in South Vietnam website (, for details of 547 Sig Tp SIGINT work in the Vietnam War.    

Operations Security (OPSEC) is another term coined during the Vietnam War by the US Military because of the failure of certain combat operations.  OPSEC is the process that identifies all critical information to determine if friendly actions can be observed by enemy intelligence.  Operation Purple Dragon starting in late 1966 by the US National Security Agency (NSA) was the origin and development of the United States OPSEC program during the Vietnam War 6.



In the early stages of the Vietnam War the US intelligence sources warned the following; 

“The enemy is conducting a highly sophisticated signal intelligence operation directed against US and Allied forces in South Vietnam.  He has developed the art of intercept to the point where his operators receive training materials tailored to particular US or Allied units against whom they working.” 7

The first US Army COMSEC unit started in Vietnam in 1960 but was only in an advisory role and one of the major lessons learned from COMSEC monitoring by the US Army was the commander’s attitude to the COMSEC analysts’ recommendations, as follows: 

a.    Paid lip service to the analyst’s recommendations, but took no action.

b.    Understood the weakness but couldn’t make changes due to the complexity of operations.

c.    Maintaining the same procedures, such as keeping the same callsigns, was poor COMSEC.

d.    Some wanted to know their mistakes and how to correct them, but they didn’t like their mistakes made public.  

US forces and 1ATF did use secure telegraph encryption links to pass sensitive information, such as dates and times for attacks, problems arose when that information was passed to South Vietnamese military and were discussed over less secure channels.  The consequences of poor COMSEC coupled with the advanced state of North Vietnamese SIGINT were serious.  The US NSA labelled the careless procedures ‘deadly transmissions’.

 104 Sig Sqn - COMSECPhoto 1A  – NVA Intercept Team       Photo 1B – US Army COMSEC Operator
(Internet sources)

The value of COMSEC monitoring is highlighted in the following US Army example:

“At one point, such operations possibly saved the life of Lieutenant General Creighton W. Abrams, the deputy chief of the US military command in Vietnam.  As Abrams was about to board a helicopter on a flight north from Saigon to Phu Bai near Hue, the details of the mission, including the time, altitude, and route, and the names of the passengers, were transmitted in the clear.  COMSEC monitors overheard the transmission and reported it immediately. As a result, the flight plan was changed.  North Vietnamese intercept operators also overheard the transmission.  Although Abrams flew by a different route, one of the other helicopters scheduled to make the trip was not told of the change.  As a result, it was shot at the whole way from Saigon to Phu Bai – an unusual effort by the VC who did not usually shoot at helicopters on such flights”. 8

Examples of enemy EW activity, both jamming and imitative deception was detail in the following extract from HQ II Field Force, Vietnam from INTSUM No 2, VC Signal Capacities, for the period 110001H to 112400H Feb 67 9.   Comment:  1ATF was under the operational command of II Field Force, Vietnam, which was a US Army Corps level command component of the US Military Assistance Command Vietnam (MACV).  The II Field Force, Vietnam HQ was at Long Binh.

104 Sig Sqn - COMSEC


1ATF Communications Security Concerns

1ATF started the hard task of setting up for combat operations at Nui Dat in Jun 1966, and establishing military control of its Tactical Area of Responsibility (TAOR).   During late 1966, the US Army provided warnings about enemy SIGINT, that the enemy had the ability to intercept 1ATF VHF and HF communications.  Also of concern, telephone voice channels were not encrypted and the 1ATF Telephone Switchboard ‘Ebony’ was connected by telephones circuits to the 1st Australian Logistic Support Group (1ALSG) in Vung Tau plus the HQ Australian Forces Vietnam (AFV) in Saigon and US Army Headquarters/Units, as well as Vietnamese operated switchboards. The Ebony switchboard operators warned 1ATF members when being connected to an external trunk telephone, that the circuit, was not secure. 

Concrete evidence for the concern of security breaches and the enemy SIGINT capabilities was found repeatedly in the Vietnam War.  For example on the 24 October 1966, 5 Platoon, B Company, 5RAR captured a female Viet Cong (VC) soldier with a US Army radio at an observation post in the Nui Dinh Mountains on Operation Bathurst.  The radio was code named “Dodo” and its location was pinpointed by the SIGINT work of 547 Sig Tp.  B Company captured a substantial amount of equipment and documents in the camp that had given the VC a panoramic view of the province, including the 1ATF base at Nui Dat.  An alert soldier of 5 Platoon saw a radio aerial strung between two trees followed the wire into a cave that lead them eventually to the radio where they also discovered the female VC clinging to the ceiling of the cave 10.

 104 Sig Sqn - COMSEC
Photo 2 - 5 Pl, B Coy, 5RAR  with female VC just after capture in the Nui Dinh Mountains
(AWM P02809.012)

 104 Sig Sqn - COMSEC
Photo 3 – Observation post captured female VC being interrogated at Nui Dat
 (AWM P01404.013)

In January 1968 there was concern with an Imitative Communication Deception (ICD) which became known as the “Australian ICD Incident” 11.  Details are as follows:

“A battalion of the 2nd Brigade, US 25th Infantry Division, was conducting a search and destroy mission, an intruder entered the battalion command net and for nearly ten hours was engaged in a running tactical exchange of information.  The intruder, purporting to be of an Australian unit operating near the 2nd Brigade declared that he wanted to establish liaison so as not to interfere with the battalion’s operations. 

The intruder gave his position as “about 23 metres” to the north of the battalion and stated he was from the “Australian 173rd Unit” on a separated search and destroy mission.  Although the intruder’s accent seemed to be Australian, although he had entered the battalion net using the battalion’s callsign, and although his methods conformed to normal Allied operational transmissions procedures, his responses to challenges and authentications were evasive.   The battalion commander, suspected an enemy ICD ruse.  The “Australian” could not have been as close as 23 metres, etc.   Keeping the “Australian” talking the battalion checked on other communications and found that there were no Australian units in Tay Ninh Province and no unit call the Australian 173rd existed.   After plotting several locations from which the intruder could be transmitting, the US battalion call in artillery fire on the areas. 

The intruder asked that the artillery cease firing on “friendly forces”.   A few more rounds of “friendly fire” and the “Australian” suddenly broke off and presumably left the scene.  A subsequent examination of the area uncovered some empty enemy base camp installations but no Australians.”

Another example one of the 1ATF battalions in 1969, captured a Viet Cong (VC) who had a AN/PRC-25 radio set tuned to the 1ATF Artillery Command Net on which all fire orders were transmitted.  The AN/PRC-25 had been captured from US Forces and allowed the enemy when a fire orders were heard enough warning time to take shelter in their tunnels and escape the onslaught 12.

7RAR Routine Orders dated 17 May 1967 13 made reference to Telephone Security issues, as follows:

104 Sig Sqn - COMSEC


1966 – Year of the Horse 14

 104 Sig Sqn - COMSECPhoto 4 – 145 Sig Sqn Radio Relay AN/MRC-69 Shelter and Antennas on Nui Dat Hill 1966
Photo supplied by John McNeil 103Sigs 21-9)

In mid-November 1966, WO2 Graham Stewart, a SIGINT specialist from 7 Sig Regt was posted into 552 Sig Tp, 145 Sig Sqn and assigned three signalmen operators (Raymond O’Brien, John Noonan and Raymond Price) for COMSEC tasks.  Graham ran a two week course for the three operators on COMSEC monitoring in Vung Tau.  Had O’Brien promoted to L/Cpl, and moved the team to Nui Dat, which would be known for over the next five years, as ‘Snoop Troop’.

At Nui Dat they had a small switchboard (SB-22) wired in parallel to the trunk circuits of the main switchboard ‘Ebony’ that serviced the Task Force.  This was the start of over five years of taping communications and reporting breaches on the radio telephone circuits connected to military forces outside 1ATF.   In addition, they also monitored the many VHF radio nets operating within the Task Force for breaches.  

Raymond O’Brien, remembers one of their first breaches located on VHF radio, was a battalion regimental radio operator manning the CP, at night, would from time to time hold the AN/PRC-25 radio handset near a civilian radio tuned to a radio station and transmit music to the deployed patrols in the tactical area of responsibility (TAOR).  While being very poor COMSEC practice, it also was effectively jamming the battalion command net.   Once reported the practice stopped!

WO2 Steward would brief HQ1ATF on issues and breaches weekly.  He remained with the COMSEC monitoring team until April 67 and then returned to the SIGINT fold at Nui Dat as the Troop Sergeant Major (TSM) 547 Sig Tp.  It has also been suggested that the original tasking for Graham may have come from Army HQ (MI8) and the Defence Signals Division (DSD).


1967 - Year of the Goat

 104 Sig Sqn - COMSEC
Photo 5 - 103 Sig Radio Operators ready to move out with 6RAR on Op Bribie. 
L-R  Sig Jim Leslie, Sgt Neil Tonkin (Det Comd) and Cpl John Chenoweth Feb 1967.  
(Photo supplied by Duncan Spencer 103 Sigs 11-19)

The Task Force Commander issued a COMSEC instruction 15 in January 1967 stating the following:

104 Sig Sqn - COMSEC

It also stated that a COMSEC monitoring team would start monitoring 1ATF communications security for breaches under the direction of the commander and can be viewed here.

No details have been located of the COMSEC reports before Jun 1967.  However members of the COMSEC monitoring team from the 145 Sig Sqn Snoop Troop return to Australian in May 1967 and were replaced with new team members from 110 Sig Sqn.   Also at the same time 104 Sig Sqn replaced 103 Sig Sqn.

In the 104 Sig Sqn war diary for Jun 1967 it details WO1 Alf Poulton (110 Sig Sqn) and Sgt Anstee (104 Sig Sqn) did a COMSEC and Anti Jamming Lecture for V Company (NZ) at the Horseshoe 16

 104 Sig Sqn - COMSEC
Photo 6 – WO1 Alf Poulton (AWM GIL/67/0697/VN)

WO1 Alf Poulton was an experienced Signal Centre Supervisor and a veteran of the Korean War and was tasked with the COMSEC monitoring within the Task Force under the direction of the OC, 104 Sig Sqn.   Alf’s first report “located” in the war for Monitoring Activities was 15-30 Jun 1967 17.  The report is as follows:

104 Sig Sqn - COMSEC

104 Sig Sqn - COMSEC
The above COMSEC Report for 15-30 June 1967 pages can be viewed here.

 104 Sig Sqn - COMSECThe above COMSEC Report for 15-30 June 1967 pages can be viewed here.

Four more COMSEC Reports by WO1 Poulton are located in the 104 Sig Sqn War Diaries, and can be viewed on the following links:

July 1967 18 View here.

August 1967 19 View here.

September 1967 20 View here.

October 1967 21 View here.

In September 1967 the OC, 104 Sig Sqn, Major Gerard Lawrence issued a paper titled ‘VC/NVA Electronic Warfare Capability’ 22 to HQ 1ATF.  Gerard in his conclusions stated:

104 Sig Sqn - COMSEC

View the full paper here.

The October 1967 COMSEC Report by WO1 Poulton included analysis of the fixed callsign systems used by the two Task Force Battalions and codes.  It also detailed problems with appointment titles for designating key personnel as inadequate and was a problem working with US forces who use an entirely different system.

Annex B to the report addressed the issues with the fixed callsigns system and codes, as follows:

104 Sig Sqn - COMSEC

Major Lawrence’s covering letter to HQ 1ATF and Staff Officer Signals (SO Sigs), AFV strongly supported changes to the system as a result of the COMSEC Detachments analysis.

HQ 1ATF issued GS Instruction 27/67 Infantry Battalion Fixed Callsigns 23 on the 9 Nov 1967 which addressed the concerns detailed in the October 1967 COMSEC Report.   
The complete instruction can be view h

In November 1967, because of the increased manpower required to man new installations in Vung Tau and Saigon, 110 Sig Sqn redeployed the COMSEC Detachment at Nui Dat to Saigon.   WO1 Poulton carried out COMSEC duties alone and his three operators were put on shift in the Major Relay Station (MRS) and Signal Centre (SIGCEN) 24.


1968 – Year of the Monkey

104 Sig Sqn - COMSEC
Photo 7 – Brig Ron Hughes, Commander 1ATF using field telephone from his forward HQ on Operation
Coburg in Bien Hoa Province Feb 1968 (AWM CRO/68/0072/VN)

This was a busy year for the Task Force and its Signal Squadron with the COMSEC Detachment working in the background without its high profile and skilled WO1 leader from 1967 who had now completed his tour. 

The detachment continue to worked at Nui Dat in 1968 but 104 Sig Sqn and 110 Sig Sqn War Diaries don’t include copies of their reports and only makes references in some monthly reports, as follows:

January 1968 25: 110 Sig Sqn

The COMSEC Det was re-constituted this month at Nui Dat.  It is currently deployed on  Operation Coburg.  Note: Detailed in the Det 110 Sig Sqn – Vung Tau Monthly Report for January 1968.

Sig Rod Barlow recalls doing COMSEC monitoring tasks on Operation Coburg and comments as follows:

“My job was to maintain a listening watch wearing headphones, constantly switching channels and recording transmissions on an Akai reel to reel tape recorder, handwriting an account of the transmission I deemed might have been a security breach.  Logging the date time and approximate location of the recording so it could be played back to the OC, 104 Sig Sqn, to determine the seriousness of the breach.

I remember recording a radio transmission from a young officer who was conveying information I considered sensitive regarding troop movements and times etc regarding the deployment of troops to FSPB Anderson (Operation Coburg).  Details were reported.

I must say that the Australian Army’s voice procedures were always excellent, unlike some procedures portrayed in Hollywood movies.” 

July 1968 26: 104 Sig Sqn

The COMSEC Det has been employed during this month monitoring the Inf Bn and the RR telephone trunk channels.  A noticeable improvement in security has occurred during the month.

September 1968 27: 110 Sig Sqn

104 Sig Sqn - COMSEC

December 1968 28 104 Sig Sqn

Monitoring has concentrated on the radio relay circuits to AFV and 1ALSG with attention to 1ATF radio nets during operations.  The standard of combinations security has continued to improve over the period. 


1969 – Year of the Rooster

 104 Sig Sqn - COMSECPhoto 8 – 104 Sig Sqn switchboard operators manning “Ebony” at Nui Dat in 1969 handling up to 6000 calls a day.  The operators warned each trunk telephone users that the circuit was not secure.
Photo supplied by Peter Diddams 104Sigs 48-16)

The COMSEC monitoring task by 110 Sig Sqn continues at Nui Dat in 1969 but without specialist equipment and problems with the maintenance of the equipment’s they had.  104 Sig Sqn was issued with secure VHF Nestor equipment which was used on the Command Net in parallel with the normal unsecured net.  104 Sig Sqn and 110 Sig Sqn War Diaries report the number of breaches but don’t have details in the monthly reports and only makes references in some, as follows:

January 1969 29

104 Sig Sqn

Specific attention was given to radio relay channels during the monitoring period via:  EMU, EBONY, ENSIGN, DEER.   No breaches were detected but a noticeable lack of use of subscribers numbers hampered operators.   13.  Due to equipment failures monitoring of VHF nets was confined to the last week of the month.  No breaches were detected.

110 Sig Sqn

A monthly report on the activities of this detachment has been submitted to the OC, 104 Sig Sqn.

February 1969 30:

104 Sig Sqn

Specific attention was given to 5RAR radio nets on that unit’s arrival in theatre.  No serious breaches were recorded.

110 Sig Sqn

At the request of the CSO a Comsec check is being carried out on the 5RAR VHF nets.  Weekly reports to be submitted to CSO via 104 Sig Sqn.  A monthly report on activities of this section has been submitted to OC, 104 Sig Sqn.

March 1969 31:  104 Sig Sqn

Radio relay channels were again monitored during March.  One breach was reported on the EBONY-ENSIGN channels.  10.  Monitoring of internal telephone systems at 1ATF gave a nil result.  11.  5RAR VHF radio nets were monitored, one breach was reported against B Coy.

April 1969 32:  104 Sig Sqn

The Task Force Comd net and Fd Regt Comd net were monitored throughout the month.  Bn nets were also monitored for a short periods.

September 1969 33: 110 Sig Sqn

Facilities at Nui Dat were improved with better RR trunk monitoring arrangements, additional recording facilities and a higher mast for VHF interception.

October 1969 34: 110 Sig Sqn

One tape recorder awaiting parts for repairs.  Replacement machine to be obtained urgently.

December 1969 35:  110 Sig Sqn

One security breach was recorded during the month and submitted to OC 104 Sig Sqn for appropriate action.


1970 – Year of the Dog

 104 Sig Sqn - COMSEC
Photo 9 – 110 Sig Sqn COMSEC Detachment member LCPL Murcott  monitoring VHF nets from the
104 Sig Sqn Communications Control bunker at Nui Dat Nov 1970 (AWM MISC/70/0820/VN)

The COMSEC Team from 110 Sig Sqn continues to monitor the Task Force radio Nets and radio relay channels while still having equipment problems and their skills being questioned, as members of the team were not trained for the task.  In July 1970 the Team was moved into the 104 Sig Sqn Communications Control bunker for closer supervision and assistance in their duties   110 Sig Sqn also started monitoring radio nets and Radio Relay channels at 1ALSG in Vung Tau.  104 Sig Sqn and 110 Sig Sqn War Diaries don’t have copies of the COMSEC reports and only makes references in the some monthly reports to the number of breaches and problems doing the monitoring task, as follows:

January 1970 36:  110 Sig Sqn

Monitoring activities were curtailed due to lack of spares for recording equipment.  Consequently very few breaches were reported.

March 1970 37:  110 Sig Sqn

Monitoring of VHF, HF nets and RR circuits continued.  A new tape recorder and additional supplies of tapes improved the efficiency of the section.

April 1970 38:  110 Sig Sqn

Monitoring of VHF, HF and RR circuits continued, breaches being reported to 1ATF via 104 Sig Sqn.

May 1970 39:  110 Sig Sqn

The monitoring team at Nui Dat was increased to three to enable more extensive coverage of VHF, HF and RR circuits.

June 1970 40:  110 Sig Sqn

The monitoring team are now working more closely with 104 Sig Sqn.  This has enabled better coverage and quicker action on breaches.

July 1970 41:   

104 Sig Sqn

104 Sig Sqn - COMSEC

110 Sig Sqn

104 Sig Sqn - COMSEC

August 1970 42:  

104 Sig Sqn

104 Sig Sqn - COMSEC

 110 Sig Sqn

104 Sig Sqn - COMSEC

September 1970 43

104 Sig Sqn

104 Sig Sqn - COMSEC

110 Sig Sqn

104 Sig Sqn - COMSEC

October 1970 44

104 Sig Sqn

104 Sig Sqn - COMSEC

Note:  Circular not located in HQ1ATF, 2RAR, 7RAR and 104 Sig Sqn Oct 1970 records.

110 Sig Sqn

104 Sig Sqn - COMSEC

November 1970 45:

104 Sig Sqn

104 Sig Sqn - COMSEC

110 Sig Sqn

104 Sig Sqn - COMSEC

December 1970 46:  110 Sig Sqn

104 Sig Sqn - COMSEC


1971 – Year of the Pig

 104 Sig Sqn - COMSEC
Photo 10 – Cpl Jeff Poulter from 104 Sig Sqn (seating) and L/CPL John McCahill from 3RAR (standing)
manning VHF radios in a bunker at Dat Do 1971.  Note the KY-38 secure equipment bottom right.
(AWM PJE/71/0114/VN)

On the 29 March 1971 Radio Troop, 104 Sig Sqn took over the COMSEC monitoring role from 110 Sig Sqn 47 of all Task Force radio nets and radio relay channels.    104 Sig Sqn and 110 Sig Sqn War Diaries don’t have copies of  any COMSEC monitoring reports and only makes references to number of breaches, monitoring equipment maintenance problems and operator training for the task in OC monthly reports , as follows:

January 1971 48:   

104 Sig Sqn

104 Sig Sqn - COMSEC

110 Sig Sqn

104 Sig Sqn - COMSEC

March 1971 49:  

104 Sig Sqn

104 Sig Sqn - COMSEC

110 Sig Sqn

104 Sig Sqn - COMSEC

April 1971 50:

104 Sig Sqn

104 Sig Sqn - COMSEC

Ken Mackenzie was the 104 Sig Sqn COMMS CON Radio Sgt and gives details on the compromises and other issues in the 104 Sig Sqn Story 79 “COMSEC, Compromises and Changing Callsigns” at: 

110 Sig Sqn

104 Sig Sqn - COMSEC

May 1971 51:  104 Sig Sqn

104 Sig Sqn - COMSEC

 June 1971 52:  104 Sig Sqn

104 Sig Sqn - COMSEC

July 1971 53:  104 Sig Sqn

104 Sig Sqn - COMSEC

August 1971 54:  104 Sig Sqn

104 Sig Sqn - COMSEC



547 Sig Tp was located in a compound within the Task Force Signal Squadron defence sector.  The troop was under operational control of the United States Army Security Agency’s 509th Radio Research Group and was assigned to the 303rd Radio Research Battalion so US SIGINT could be relayed to 1ATF.  The troop did direct SIGINT support for 1ATF and US forces operating under IIFFV command. 

The work of the troop was marked with great secrecy and very few individuals outside it knew of its real role or could access its reporting. 

 For details of 547 Sig Tp in South Vietnam see:

 104 Sig Sqn - COMSECPhoto 11 – 547 Sig Tp Set Room at Nui Dat.  Monitoring enemy Radio Traffic 1969.  
(Photo supplied by Roy Dean 547Sigs 4-2)

Many in 1ATF through the troop was doing COMSEC monitoring and labelling them 'Cobber Dobbers'.  US forces used the term 'Buddy Fuckers' for their COMSEC teams. 

104 Sig Sqn SNCOs were most likely happy not to correct their young soldiers about the 547 Sig Tp real tasks.  This kept the Radio Operators, which included many national service signalman, as well as lots of regular soldiers, all with limited military experience using correct procedures on their Radio tasks.

The 110 Sig Sqn COMSEC team from Snoop Troop didn’t broadcast their role at Nui Dat also.


Secure Voice Equipment

US Forces 55

In the field, standard security measures, such as the manual encryption and decryption of messages, made communications slower and more complicated, a distinct disadvantage in the heat of battle. To make things easier, voice security equipment for stationary and vehicular radios, known as KY-8, began reaching tactical units in 1965. Unfortunately, this device not only reduced transmission range but also generated a great deal of heat.  Security equipment for aircraft radios, designated KY-28, and for manpack or mobile use, KY-38, became available in 1967. The latter, in combination with the AN/PRC-77 radio, weighed fifty pounds, a significant burden for the foot soldier.

104 Sig Sqn - COMSEC
Photo 12A – Nestor TSEC/KY-8         Photo 12B – Nestor TSEC/KY-28 (with KYK-28 Key Gun). 
Photo 12C – Nestor TSEC/KY-38 (with KYK-28 Key Gun) - (Internet sources).

Australian Task Force

1ATF received the first KY-38 equipment’s for the VHF Command Net in April 1969 and were deployment with the three Battalion 104 Sig Sqn detachments and the SAS Sqn 152 Sig Sqn Detachment 56.  The equipment was used on a “demand’ basis and was proved quite successful.  By 1971 the VHF Command Net Secure was important to Command and Control of the Task Force.



COMSEC is a balancing act in battle between saving lives and taking the fight to the enemy.  During the battle little SIGINT is gained by the enemy that has long term value.  However it would appear our combat troops were trained well and used adequate COMSEC practices in most situations. 

The COMSEC monitoring team from 110 Sig Sqn was only as good as the expertise of its members and the detachment leader.  Clearly WO2 Graham Stewart and WO1 Alf Poulton at the beginning of the COMSEC monitoring in 1967 were most experienced.  Poulton report in October 1967 is a good example of his skills which was instrumental in changing the callsign schema used by 1ATF battalions.   After 1967 team leaders and members, appeared to not have the high level skills and operational experience required for the task.  In addition, the team lacked specialist equipment used by the US Forces for their task.   However because monitoring was undertaken of the 1ATF communications, breaches reported and passed back to units commanders, this helped maintain adequate COMSEC within 1ATF.

Did the US NSA monitor our Task Force communications?   No details have been located but it is assumed they did. 

Secure Voice Equipment used on the 1ATF Secure VHF Command Net in the final years of the deployment would have helped reduce the risks of high level COMSEC breaches.   However information from the secure net could have been passed down into sub units.  Therefore there was always a COMSEC risk within the Task Force when a skilled enemy in SIGINT was at work.  

Australian trunk telephone systems were never encrypted and our systems manually connected into most Allies Systems in the Vietnam theatre.   It was very wise to warn users it was unsecure, as this was a high use media, which many members of the Australian Force didn’t understand the security risks.  However it should be noted that the US Army command telephone link from HQ1ATF to HQIIFFV were encrypted by 1970.

No details of OPSEC being conducted by AFV or 1ATF, was located in the research for this story, like the NSA Operation Purple Dragon.  As the Australian force operated as part of the US force it must be concluded that OPSEC for the Australian force was assessed also under Operation Purple Dragon.  However unlike the US Army, only very limited access for Vietnamese was allow at our combat base Nui Dat.   This was a real advantage in its physical security.   However, Vietnamese civils were employed at 1ALSG at Vung Tau and this may have been an issue.

From the research of the records it is clear COMSEC monitoring was occurring at the Task Force and being reported to the HQ1ATF but no details are recorded of how the breaches were passed to unit commanders and what actions they took to correct poor COMSEC within their units.    Maybe like the US Forces, unit commanders wanted to know their mistakes and how to correct them, but they didn’t like their mistakes made public. 



1.     An ancient military axiom.

2.     PURPLE DRAGON: The Origin and Development of the United States OPSEC Program (Page 13).

3.     Force Signals (145 Sig Sqn replaced by 110 Sig Sqn) provided the communications rear of 1ATF including back to Australian.

4.     Task Force Signals (103 Sig Sqn replaced by 104 Sig Sqn) provided the communications for HQ1ATF.

5.     AWM95-6-2-3 104 Sig Sqn - Standing Orders, Unit Security Instructions (Annex D) paragraph 27.

6.     PURPLE DRAGON: The Origin and Development of the United States OPSEC Program (Page V).

7.     Book:  Body of Secrets (Page 304) by James Bamford

8.     Book:  Body of Secrets (Page 306) by James Bamford

9.     AWM95-6-4-13 145 Sig Sqn – Extract from HQ2FFV INTSUM No 42, VC Signal Capacities.

10.   Photo details at

11.   Book: Southeast Asia ‘Working Against the Tide” (Pages 8 to 11) by Wolfe, Schmidt and Thompson

12.   Signals Swift and Sure (Page 236) by John Blaxland

13.   AWM95-7-7-3 7RAR (Page 115) Telephone Security

14.   Based on emails from Robert Hartley AM and telephone interview with Raymond O’Brien Feb 2020.

15.   AWM95-1-4-24 HQ1ATF – COMSEC Instruction (Page 176-178)

16.   AWM95-6-2-3 104 Sig Sqn - COMSEC and Anti Jamming Lecture for V Company (NZ)

17.   AWM95-6-2-4 104 Sig Sqn – COMSEC Report 15-30 June 1967

18.   AWM95-6-2-5 104 Sig Sqn – COMSEC Report July 1967

19.   AWM95-6-2-6 104 Sig Sqn – COMSEC Report August 1967

20.   AWM95-6-2-7 104 Sig Sqn – COMSEC Report September 1967

21.   AWM95-6-2-8 104 Sig Sqn – COMSEC Report October 1967

22.   AWM95-6-2-7 104 Sig Sqn – VC/NVA Electronic Warfare Capability Paper

23.   AWM95-1-4-68 HQ 1ATF – GS Instruction 27/67 – Inf Bn Fixed Callsigns – See pages 58-60

24.   AWM95-6-3-7 110 Sig Sqn – November 1967 Monthly Report, COMSEC team redeployed to Saigon.  See Para 9.

25.   AWM95-6-3-9 110 Sig Sqn – January 1968 Det Vung Tau Monthly Report, COMSEC Para 7.

26.   AWM95-6-2-16 104 Sig Sqn – July 1968 Monthly Report, COMSEC Para 8.

27.   AWM95-6-3-17 110 Sig Sqn – September 1968 Monthly Report, COMSEC Para 36.

28.   AWM95-6-2-21 104 Sig Sqn – December 1968 Monthly Report, COMSEC Para 6.

29.   AWM95-6-2-22 104 Sig Sqn – January1969 Monthly Report, COMSEC Para 12
and AWM95-6-3-21 110 Sig Sqn – January 1969 Monthly Report, COMSEC Para 20.

30.   AWM95-6-2-23 104 Sig Sqn – February 1969 Monthly Report, COMSEC Para 8

and AWM95-6-3-22 110 Sig Sqn – February 1969 Monthly Report, COMSEC Para 32.

31.   AWM95-6-2-24 104 Sig Sqn – March 1969 Monthly Report, COMSEC Para 9.

32.   AWM95-6-2-25 104 Sig Sqn – April 1969 Monthly Report, COMSEC Para 10.

33.   AWM95-6-3-29 110 Sig Sqn – September 1969 Monthly Report details COMSEC Para 11.

34.   AWM95-6-3-30 110 Sig Sqn – October 1969 Monthly Report, COMSEC Para 15.

35.   AWM95-6-3-31 110 Sig Sqn – December 1969 Monthly Report, COMSEC Para 16.

36.   AWM95-6-3-32 110 Sig Sqn – January 1970 Monthly Report, COMSEC Para 7d.

37.   AWM95-6-3-33 110 Sig Sqn – March 1970 Monthly Report, COMSEC Para 8d.

38.   AWM95-6-3-34 110 Sig Sqn – April 1970 Monthly Report, COMSEC Para 11.

39.   AWM95-6-3-35 110 Sig Sqn – May 1970 Monthly Report, COMSEC Para 8.

40.   AWM95-6-3-36 110 Sig Sqn – June 1970 Monthly Report, COMSEC Para 8

41.   AWM95-6-2-40 104 Sig Sqn – July 1970 Monthly Report COMSEC Para 5
and AWM95-6-3-37 110 Sig Sqn – July 1970 Monthly Report COMSEC Para 19, 20 and 21.

42.   AWM95-6-2-41 104 Sig Sqn – August 1970 Monthly Report COMSEC Para 5
and AWM95-6-3-38 110 Sig Sqn – August 1970 Monthly Report COMSEC Para 20 and 21.

43.   AWM95-6-2-42 104 Sig Sqn – September 1970  Monthly Report COMSEC Para 7
and AWM95-6-3-39 110 Sig Sqn – September 1970 Monthly Report COMSEC Para 18g.

44.   AWM95-6-2-44 104 Sig Sqn – October 1970 Monthly Report COMSEC Para 6
and AWM95-6-3-40 110 Sig Sqn – October 1970 Monthly Report COMSEC Para 16g.

45.   AWM95-6-2-45 104 Sig Sqn – November 1970 Monthly Report COMSEC Para 6
and AWM95-6-3-41 110 Sig Sqn – November 1970 Monthly Report COMSEC Para 14g.

46.   AWM95-6-3-42 110 Sig Sqn – December 1970 Monthly Report COMSEC Para 16h

47.   AWM95-6-2-48 104 Sig Sqn – 29 March 1971 110 Sig Sqn COMSEC team at 1ATF replaced by 104 Sig Sqn Radio Troop personnel.

48.   AWM95-6-2-46 104 Sig Sqn – January 1971 Monthly Report COMSEC Para 25, 26 and 27
and AWM95-6-3-43 – January 1971 Monthly Report COMSEC Para 16i

49.   AWM95-6-2-49 104 Sig Sqn – March 1971 Monthly Report COMSEC Para 30, 31 and 32
and AWM95-6-3-45 – March 1971 Monthly Report COMSEC Para 17k.

50.   AWM95-6-2-50 104 Sig Sqn – April 1971 Monthly Report COMSEC Para 18, 18 and 20
and AWM95-6-3-46 110 Sig Sqn – April 1971 Monthly Report COMSEC Para 27.

51.   AWM95-6-2-51 104 Sig Sqn – May 1971 Monthly Report COMSEC Para 21, 22 and 23.

52.   AWM95-6-2-52 104 Sig Sqn – June 1971 Monthly Report COMSEC Para 26 and 27.

53.   AWM95-6-2-53 104 Sig Sqn – July 1971 Monthly Report COMSEC Para 20 and 21

54.   AWM95-6-2-54 104 Sig Sqn – August 1971 Monthly Report COMSEC Para 22

55.   Getting the Message Through, The Vietnam Conflict Chapter X Page 369 by Rebecca Robbins Raines See

56.   AWM95-6-2-25 104 Sig Sqn – April 1969 Monthly Report details KY-38s issued for secure communications.


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