Battle of Long Tan (1966)

and Signals Intelligence (SIGINT)


By Denis Hare OAM BEM


Vietnam Veteran’s Day is a special day where we remember the involvement of Australians in the Vietnam War from 1962 to 1975.   It is held on the 18th August each year on the anniversary of the Battle of Long Tan.

The Battle of Long Tan was not our first or largest Battle involving ANZAC Troops in the war, however it is our most savage and decisive engagement of the Vietnam War, earning both the United States and South Vietnamese Presidential Unit Citations for gallantry along with many individual awards.

In the battle, more than 245 Viet Cong and 18 Australians were killed. 

Battle Overview

The Australian operations base at Nui Dat, in Phuoc Tuy Province, was fired upon by the Viet Cong with 82 mortar rounds at about 2 am on 17th August 1966.  24 Australians were wounded, two seriously.

On 18th August, D Company, 6RAR, numbering 105 Australians and a three-man New Zealand artillery team, was sent into the Long Tan rubber plantation, and came under heavy machine-gun fire and mortar attacks from Viet Cong - estimated to be at least 1,500 and possibly 2,500 troops.  D Company commander, Major Harry Smith, requested resupply of ammunition and troop reinforcements.  Nearly out of ammunition, at 6 pm two UH-1B Iroquois (Huey) from No. 9 Squadron RAAF arrived overhead, in the blinding monsoon heavy rain, to resupply D Company by dropping ammunition wrapped in blankets thru the rubber trees.

Long Tan Action by Bruce Fletcher
Painting “Long Tan Action” by Bruce Fletcher which is at the AWM (AWM ART40758)

The combination of aggressive fire from D Company soldiers plus devastating artillery fire from Nui Dat had swung the battle in the Australians’ favour but the Viet Cong continued to manoeuvre to gain the upper hand.  Meanwhile, A Company from 6RAR had been ordered to move to the support of the beleaguered D Company.

After almost three hours of intense fighting by D Company, reinforcements from A Company arrived in armoured personnel carriers (APC).  Ammunition was distributed and the wounded were tended. The extra fire-power finally stopped the Viet Cong, and all firing ceased.

18 Australians were killed in action - 17 from D Company and one from the 3 Troop, 1st Armoured Personnel Carrier Squadron - and 21 wounded.   The Viet Cong insurgents left 245 dead and many more wounded.  In later years, it was found that D Company had run into a reinforced regimental force waiting to attack Nui Dat.

Signals Intelligence (SIGINT)

Highly classified for many years was the radio work of a specialist small Signals Unit at Nui Dat, involved in SIGINT, 547 Signal Troop (547).  In the lead up to the Battle of Long Tan, 547 identified the radio callsign of 275 (VC) Main Force Regiment, a fresh unit to Phuoc Tuy Province and under the control of HQ 5 (VC) Division. 

The 547 operators located the transmitter of 275 Regiment a couple of kilometres north of Xuyen Moc, it then approached the Nui Dat base in steady deliberate stages, as though moving tactically, taking sixteen days to cover the seventeen kilometres from there to the area of Nui Dat 2 (near Long Tan), with 547 operators locating the transmitter twelve more times along the way from the 2 to 14 August.

That, in the Troops opinion, should have stirred the staff at the Headquarters (HQ) of the 1st Australian Task Force (ATF).  It caused hardly a ripple.

In his 16 September verbal report to MI8, Capt Richards stated: As a matter of interest, on this attack with the 275th Regiment, we did produce some useful intelligence through the ARDF fixes in that the Brigadier was warned that the 275th was moving towards our direction, and although we didn’t know exactly where he was because the only transmitter we could fix on the whole Regiment was the rear—link working back to Division we then had no idea where the actual Headquarters itself was or the Battalions.

Comment:  It must be stressed that in 1966, 547 did not have any organic DF capability.  All DF fixes were supplied by the USAF or US Army.  In research by Bob Hartley with the AWM, ASD, and discussions with the Americans, Bob was not able to locate any fix data for the period.  There is no record – twelve fixes looks like being a bit of a furphy.  USAF records for the period show that a total of 23 fixes were passed to ground stations during Operation Toledo (all of August) which covered the area where 275 and other units were operating.

 Movement of 274
Movement of 275 Regiments transmitter towards Nui Dat as detailed in the Book
'To Long Tan: Australian Army and the Vietnam War 1950-66' by Ian McNeill 1993'
 (29 Jul 1966 to 14 Aug 1966

One of the problems was the little understanding, by the staff of HQ 1 ATF of the importance of information provided by 547 Signal Troop at the time.  Also only four people outside the Troop at Nui Dat, were authorised to be told the sources of 547's information (The Commander, Operations Officer and the G2 plus G3 Int) by the Australian Department of Defence.  US intelligence came in reams, but often it was not parochial enough for the Task Force, so most reliance was placed on reports from Australian sources, especially patrols.  Also the Task Force HQ treated intelligence from the South Vietnamese Army and Police as suspect due to the conflicting nature of their reports.

On the 18th August 1966, D Company, 6 RAR, near Long Tan fought a the battle, with over two thousand enemy.

547 Sig Tp Set Room 1966
547 Signal Troop Set Room at Nui Dat (1966)

 At 5pm as the besieged D Company were requesting a desperate resupply of ammunition by helicopters, another significant event occurred.  The Commander, at last, called the OC of 547 Signal Troop to his side and asked for his analysis of the enemy attacking D Company.

Richards had no problem responding in detail, relieved that his team efforts had, at last, won recognition. 


If the SIGINT from 547 Signal Troop had been understood by the Task Force, maybe we would not have lost 18 young Australians on the 18th August 1966.  However the fog of war will always be present!

SIGINT and Electronic Warfare (EW) plus the computerised flow of information, are now vital elements of any military involvement, operating down to patrol level with satellites, aircraft (including unpiloted), imagery, communication monitoring and remote senses assisting the troops, with their missions.  

Denis Hare

August  2014

 Additional Information:

 1.    Artillery: The guns at Nui Dat fired almost non-stop for over 5 hours in support of the battle.  The guns from the 1st Field Regiment, Royal Australian Artillery involving all eighteen Italian L5 Pack Howitzer 105mm (twelve Australian and six New Zealand ) firing at times regimental fire missions  and at some stages all six US guns from A Battery, 2/35th Artillery Battalion using M109 Self-propelled 155mm Howitzers.  This was the first regimental fire missions fired by the ANZAC’s since the Korean war and will probably never be fired again.   Artillery fire was eventually brought in “Danger Close” to within 50 metres of the Australian positions.  Lightning twice hit the artillery positions and two artillery gunners passed out from cordite fumes.  Over 3500 rounds were fired during the battle and US Army Chinooks helicopters flew ammunition to Nui Dat, during the night of the battle, to replace the rounds used.

105 Guns
Italian L5 Pack Howitzer 105mm (front) with the L2A2 Howitzer 105mm (rear) that replaced the Pack Howitzer after the Battle of Long Tan.  Guns photograph at the National Vietnam Veterans Museum, Phillip Island.

2.    Aircraft:   The two Huey UH-1B aircraft (A2-1020 and A2-1022) were flown without RAAF operational approval to get the ammunition to D Company.  No other aircraft were involved because of the very poor weather, at the battle site, until midnight.  Then the first of seven RAAF Huey’s landed, at an improvised landing zone, on the edge of Long Tan rubber, to start the medical evacuations of our wounded and dead.     Huey A2-1022 has been restored cosmetically and is now proudly sitting just above the trees, in the memorial garden at Caloundra RSL. The aircraft was used as a prop in the movie on the Battle of Long Tan  'Danger Close' in 2019.

Caloundra RSL A2-1022
Huey A2-1022 at Caloundra RSL

3.    Signals:   The enemy communications were in morse code.  The radio command net and the other communications systems vital to the control of the battle, evacuation, notifying Higher Command and Australia (NOK, etc), performed without fault, which was vital to the conduct of the battle.  It was a credit to the Royal Australian Corps of Signals involved; 103 Signal Squadron (Task Force Signals) and 145 Signal Squadron (Force Signals).  547 Signal Troop from that day, the Australian 'Agency' charged with passing on US information quietly became an agency producing and passing on its own SIGINT back to US authorities, as well as the Task Force.  Over the period of the war, its work saved many Australian and American lives.   Currently there is an ongoing inquiry by the Defence Honours and Awards Appeals Tribunal into the recognition of service with 547 Signal Troop, in Vietnam, from 1966 to 1971 with the award of a Meritorious Unit Citation or another form of medallic recognition for their service.  

547 Sig Tp   103 Sig Sqn Radio Ops
Photo (Left):  VC Morse Operator     Photo (Right):  103 Sig Sqn Radio Operators

4.    Republic of Vietnam Cross of Gallantry with Palm Unit Citation:  On the 1st September 2018 the Governor-General, His Excellency General the Honourable Sir Peter Cosgrove AK MC (Retd), formally approved the awarding of the Republic of Vietnam Cross of Gallantry with Palm Unit Citation (the citation) to members of 547 Signal Troop in recognition of the military assistance provided to the former Republic of Vietnam (South Vietnam) while under the operational command of the United States Military Assistance Command (MACV).

547 Sig Tp


1.  Army 'Our History Website' story on Long Tan.

2.  Pronto in South Vietnam

3.  Battle of Long Tan and Vietnam Facts from many Internet sources.

4.  Email with additional information from Bob Hartley (Ex 547 Sig Tp, SVN) dated 28 May 2016.

5.  Email with additional information on the guns from Colin Flatters Ex 103 Fd Bty, SVN) dated 28 July 2016.

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