DETATCHMENT 131 DIVISIONAL LOCATING BTY (SVN)

South Vietnam (SVN) 1966 TO 1971

Locating Artillery, possibly one of the least known or understood units that served in South Vietnam, was a vital component of Australian Artillery and played a major, though often low-key role in its assistance to 1ATF. Detachment 131 Divisional Locating Battery (Det.131) members' duties found them dispersed throughout Nui Dat and Horsehoe locations.

On 6 June 1966 (6/6/66) 1st Australian Task Force moved to Nui Dat, included was Det. 131 During the tenure in South Vietnam until August 1971, regardless of Operations, R and R, R and C or change over of personnel; the unit maintained a 24-hour support/watch of 1ATF (possibly the only unit to do so), earning the locators the motto " Eyes of the Task Force". In all 463 Locator's served with Det. 131 over a period of five years and two months (1886 days) With never more than 100 members in country at one time.

Det. 131 held a unique distinction amongst Australian Artillery units in SVN, in that it became the only Artillery unit in which individual replacement of personnel took place. In other units, Btys and HQs were rotated completely. To assist in administration the unit laid nearly forty mile of cable to its sections and installed its own telephone exchange at the new HQ with line laid to all Listening Posts ( LPs ), radar command posts, Arty Tac and survey living area. In the period 1966 - 1971:

1. Det 131 suffered one accidental death, 1 KIA, 8 WIA.
2. The survey section provided survey for over one hundred Fire Support Bases, established a common grid for all indirect fire weapons in the task force area and surveyed registration points. It provided support to the Australian, New Zealand, US and the Republic of Vietnam forces.
3. The Radars and Arty Int Sections (LPs) deployed to over 100 FSBs as well as manning a Radar and a minimum of two LPs on a twenty four hour basis at Nui Dat.
4. The Task Force Artillery Intelligence Office (TFAIO) which was deployed at Nui Dat Tac HQ RAA maintained 24/7 Arty Int Team which collected ,collated and distributed Intelligence Data ( Mainly Artillery Intelligence) from and to the many end users.
5. Det 131 was an authorised Artillery Observer. Therefore could request and control fire (Carry out visual or electronic adjustment of rounds fired onto the target) from all sources of Artillery and Infantry Mortars. The unit also had Authority to conduct Air Strike missions onto selected targets.
6. The majority of the unit was cross trained Eg;
" Artillery Intelligence (Arty int) operators were also trade tested as Artillery Signalers and many would be trade tested drivers. They may also be trade tested Radar operators.
" Many Surveyors would be trade tested Drivers and/or signalers in the later part of the conflict they also became Sound Ranging operators.
" Radar Operators were also Arty Int operators Drivers and Signalers.

The Arty Intelligence Office was deployed at 1 Fd Regt Tac (Tactical) HQ.RAA with the initial employment of LPs sited with 5 RAR, 6 RAR and 1 Fd Sqn RAE. The Radars deployed south and west originally co-located with 105 Fd Bty and 103 Fd Bty, scattered throughout the Task Force Area, this was to be the deployment pattern for the unit for the years to follow.

The first location of an Enemy Mortar by Det 131 in SVN occurred on the night of 6/6/66. About 2000hrs, a clearing patrol was fired upon by an enemy mortar south east of Nui Dat. Radio call sign (c/s) 21A (Alpha Radar) was actually laid on a bearing, which coincided with the direction of the mortar. Although the computer was not functioning correctly and the servo drives for the antenna failed to work, Alpha was able to determine a range and bearing from which the grid reference could be obtained. The Radar No.1 sent in a Locrep (Location Reports, included the Grid Reference of the enemy weapon) to Arty Tac and at the same time alerted his mates in 103 FD Bty to come to a stand-by bearing. Counter Battery (CB) fire was ordered from 103 Fd Bty and the mortar position fell silent. Although the No 1 was congratulated for his quick thinking, he was also reminded firmly that there was a correct reporting method, which must be used in future.

During this period until end June 1966, four further Locreps on enemy mortars were obtained from the Radar's. Air strikes were ordered on three of these Locreps, and carried out by USAF, SVNAF, and USN aircraft. As a result no further mortaring was recorded from these locations.

Apart from deploying the Radars and Lp's the Arty Int staff were far from idle, examining aerial photos, picto maps and intelligence reports and gathering data on the types of weapons the Task Force would likely to encounter. Cracker and Cracker Minor (the radio callsigns for the TFAIO and assistant TFAIO) and their staff determined from information available that the enemy was not a sophisticated gunner, even though there appeared to be many weapons available to the enemy their popular choice and therefore the main threat was the Chicom 82mm Mortar. What made this weapon the main threat was the simplistic methods used to deploy and fire this mortar. From reading interrogation reports from the various sources available to Arty Int, it was understood that in many cases the distance to the target was paced out by a local under the guise of looking for his buffalo or family etc, the mortars therefore fired at a fixed elevation because the range that they were fired from seldom varied. Some physical feature was used as an aiming point, for example a track or tree line or creek line etc was always pointing along the line of fire. It would follow from this that there was no survey capability whatsoever. Knowledge of the firing table for the 82mm Mortar and Crater Analysis soon told us where to expect fire to originate from. This became the Basis of the CB fire plan which was distributed to all gun positions; some of these targets were included in each nights H (Harassment) and I (Interdiction) missions. This information was also a major consideration when Line Alpha was created around the Task Force area.

Line Alpha was integral to the defence of Nui Dat and a major factor in its development was the maximum range of an 82mm mortar. This was the guide to drawing line Alpha this distance out from the perimeter defences, later the area between Perimeter and Line Alpha became known as the 'Exclusion Zone'.

A Bty - 2/35 US Artillery (US 175mm SP guns) was attached to 1 ATF and established a position in the Southwest corner of the TF. Det. 131 deployed its fourth LP with this Bty (31D LP). (See Photo)

Operations Hobart 1 and Hobart II were conducted in the Long Tan area east of Nui Dat by 6 RAR from 24 July to 29 July 1966. During these operations 6 RAR came under mortar attack. Mortreps were received from two of Det. 131 LPs, 1 Fd Sqn and elements of 6 RAR. The TFAIO produced a Locrep, based on bearings from the Mortreps, upon which 1st Fd Regt conducted CB fire.

LP work was a monotonous job most of the time and as such many types of reps (Reports) would flow into the Arty Int office much to the delight of the Int Staff. There were over the years Buffaloreps, Pigreps, Dogreps, peoplereps, and lightreps to name just a few, However one lightrep turned out to be a very serious matter.

Cracker minor, was on night shift when he received a Lightrep from the LP perched on top of Nui Dat (31A LP see Photo ), the CO of 1 Fd Regt happened to be in the command post at the time and ordered a fire mission because the report put the light inside line Alpha, six rds Fire For Effect ( FFE ) were ordered from the Regt, The LP operator was the observer and corrected the fall of shot and 'Repeat' (artillery Fire order meaning to fire the original order again) was ordered, the light was extinguished and the Regt had expended 216 rds of ammo. Cracker Minor stayed tightlipped in the command post but later spoke to the LP operator and asked him if it was a genuine report, the operator assured him that it was.

As a footnote to this incident after the war had finished, a former local VC fighter recalled how his section in 1966, had been ordered to locate and map the Australian strong points (Heavy/ Medium machine gun positions) and so devised a plan to put lights on the end of long poles to draw the fire, however no machine gun fired and they had to flee when Artillery rounds started to arrive.

After each mortaring, weather it be on the TF or a local forces compound Det 131 would dispatch a Crater Analysis Team to inspect the mortar craters (much information could ascertained from craters) after one such excursion, the team leader reported the following; I was called out to conduct crater analysis at an ARVN outpost ( see Photo ) to the north of Nui Dat after it was mortared the previous evening, I found approx 20 craters in excellent condition and after examination I was able to suggest a grid ref of the firing point. The Australian adviser informed me that one bomb had not detonated on impact and I was interested to see if I could verify the country of manufacture of the 82mm bomb and perhaps gain more information from it and asked to see it, I was horrified to see that one of the ARVN soldiers was using the UXB to drive in star pickets. However upon examination I saw that it had been fired without a fuse and often wondered how the person who carried the bomb all the way down the Ho Chi Min trail would feel if he knew that some dope had forgotten to put a fuse in before it was fired. I was delighted the next day when I received a message from the Aussie Adviser stationed at the outpost that the position indicated was spot on and they had discovered the tube and a cache of ammunition nearby. The downside was that whenever I was required to conduct crater analysis in that area again, most of the craters were tampered with to recover the tail fins and fuses for keepsakes.

Battle of Long Tan
On the night of the 16/17 Aug 1966 at 0204 hrs the Task Force Base at Nui Dat, came under attack from mortar fire and a 70mm gun. This gun was identified the following morning from fragments and one unexploded round located by Arty Int Operators, as a Japanese WWII 70mm mountain Howitzer. This type of gun weighs 450 lbs (200 kg) and can be very quickly dismantled into 3 pack loads. The weapon was never found although the possible firing position was located. No further encounter with this type of weapon occurred throughout the remainder of the conflict.

A total of 67 82mm mortar craters were located in the following areas,
" Arty Units 16
" 1 Fd Sqn 16
" 3 SAS Coy 10
" 1 ARU 25
The southern edge of 103 Bty and 161 Bty RNZA received 5 70mm rounds.

Retaliation fire commenced seven minutes after the attack began under a CB fire plan that was then in force. CB fire took place in the following order:

Targets on Locreps (no Locreps were obtained from the Radars with only 21 B functioning)
Targets at likely firing positions obtained by Mortreps from LPs (this constituted the first fire mission)
Targets on likely withdrawal routes
Targets obtained from observation other than a Mortrep.
During this attack Det 131 received its first battle casualty's two members wounded by shrapnel (WIA), Crater Analysis was conducted early on the morning of 17 August 1966 with about one third of the craters in condition sufficiently pristine to extract results.

The TFAIO combining the information from the previous night and the results from the Crater Analysis determined there had been four possible base plate positions. The position where the majority of fire originated from was assessed as coming from the southwest with a second position some 3-400 metres further to the south. The other two locations were in the east and southeast. A request was sent from TFAIO to TF Command that these positions be visited to gather any intelligence that may be found.

B Company 6 RAR was dispatched to the southwest to investigate the first two suspected areas and upon return confirmed they had located a mortar base plate position, which had contained at least four base plates (Firing positions) with weapon pits for thirty-six men. The area was covered by a number of shell craters results of the counter Mortar fire. If the effectiveness of the CB fire plan needed proving then this one sight alone would be all that was needed as one firing position was discovered with blood trails and ruined recoilless rifles, and as no recoilless rifle rounds were received in the TF area it appears they were neutralised before firing a round. The position was approximately 100 metres southeast of the first regimental target engaged the previous night.

B Company also investigated an area 300 metres south of the base plate position and confirmed that there had been activity in this area, but there being a large amount of recent shell craters it was not possible to confirm the location as either mortar or gun position.

On 18 Aug 1966 D Company 6 RAR commenced Operation Smithfield, a search and clear mission in the Long Tan area. Part of this mission was to locate the two remaining base plate positions in the east and southeast locations.

At around 1540 hrs, 11 platoon D Company 6 RAR became engaged in a firefight with a small VC patrol. This would lead to an engagement with a much larger enemy force.

The ensuing conflict became known as "The Battle of Long Tan". During the Battle members of the Detachment (and many other unit personnel) assisted the batteries of 1 Field Regiment with ammunition resupply

On 28 Oct 1966 two surveyors were attached to the Meteorology Team of A Bty 2/35 Bn (US) for training in Air Temperature and Density computer, Ballistic Winds Plotter and Zone wind Plotter. This was 131s first dalliance with Light Meteorological activities.

Operation Hayman

Commenced on the 6 November 1966, 5 RAR was to conduct a search and destroy mission on Long Son Island, and a fire support base on the mainland would support them. This would be the first time that all the operational sections of Det. 131 were deployed outside 1 ATF base. No survey was requested for this fire support base and theatre orientation was provided by the simultaneous observation method for the guns and the Radar. Three LPs were deployed as follows:

" LP 31 to cover the north and west of the island.
" LP 34 to cover west to south.
" LP33 with B coy 5 RAR, to cover north and east.
The Arty Int. section was deployed with the forward Arty Tac HQ and Alpha Radar was deployed in the FSB with 103 Fd Bty. Throughout the mission the LPs gave excellent coverage and reported on a number of incidents, however no mortars were located on the island. Operation Hayman was completed on 12 November 1966.

On 16 Nov 1966, 9 surveyors from Det 131 were detached for field work with 1 Topo Svy Det, along with 3 surveyors from 2/35 US Arty who were to provide a common grid to US and ARVN guns

On 18 November 1966, Operation Ingham a Search and Destroy mission east south east of 1ATF was commenced by 6 RAR. Survey was requested on this operation for three gun positions

The early months of 1967 saw the 131 Survey Section carrying out many survey tasks, including surveying new control points for A Bty 1st 83rd Bn (US) and 6 control points at the "Horseshoe" feature.

Together with Det. 1 Div Topo Svy Tp, members of Det.131 Survey Section established control points on theatre grid and passed the information to the guns, radars and mortars, thus placing them on a common grid

The survey section comprised a section HQ, six observing pairs, two computing pairs and four vehicles. During April 67 a number of members from the Survey section were 'lent' to Topo Survey to conduct experiments into the feasibility of a helicopter airborne satellite station for long distance survey. The scheme was never completed due mainly to faulty equipment and a lack of available protection. This scheme would be revisited by the detachment survey party and refine the procedure to a stage where airborne fixation by Helicopter became a normal practice and would later be taught at the School of Artillery. When the Horseshoe Feature was surveyed a variation was used whereby two Hydrogen filled met Balloons were anchored and floated at 80 feet to achieve a ground fix.

June and July 1967 were also the survey section were to take part in Operation Paddington. They would supply fixation and orientation to four Fire Support Bases:

" Tom
" John
" Bill
" Mike
On 13 Jul 1967 enemy mortars fired upon FSPB Mike, and a Radar operator received shrapnel wounds. He was evacuated by "dust off" (helicopter) to Blackhorse General Hospital (US) and returned to Australia on 14 Aug 1967.

During the later part of 1967 the Det. 131 became very much involved with the many operations being conducted with LPs, Radar and Survey assisting on Operation Ainslie, Operation Kenmore and Operation Santa Fe.

0n 3 Nov 1967 Bravo Radar along with LP 31D was air lifted into FSPB Lion by CH47 (Chinook) Helicopter, this was the first operational airlift of an AN/KPQ-1 although a number of in country trials had previously been conducted. The airlift of the equipment was accomplished in two lifts:

On 5 Nov 1967 a second LP 31G arrived at FSPB Lion. This was a composite LP and comprised two members from Arty Tac and three surveyors.

At 2015 hrs on 6 Nov 1967 FSPB Lion came under attack from Viet Cong Forces, with probing attacks by ground forces from three sides supported by mortar fire. This attack occurred when the FSPB was conducting its own Defensive Fire (DF) and as the majority enemy rounds fell short of the Fire Support base there was some confusion as to what was occurring.

The ground attack was short lived and no breaches of the wire were reported, it was not until the craters were found the following morning (12 X 82 mm) that it was confirmed that the action had actually taken place.

As the Australian operations started to expand beyond the immediate Nui Dat area, and the batteries began to deploy further a field, this increased the problems of providing both fixation and orientation. Apart from the greater range to be covered the dense jungles meant the survey schemes increased in size and complexity.

The danger of attack by enemy forces on isolated pairs strung out along a survey scheme, increased and rarely could protection forces be spared, because normally the survey work was conducted concurrent with deployment of guns, and hence their most vulnerable time.. Another problem arose when it was found that most maps were not adequate. The fire trails (cleared trails through the jungle) were not always accurately shown on maps, yet in many cases these were the only recognisable features on the map. (In 1969 one fire trail junction was proven by survey to be some 1000 metres in error).

I Div Topographical surveyors had formed a close working relationships with the 131 surveyors and co operation began on overcoming the problems of close country survey over longer distances. Two techniques were developed; synchronised astronomical observation to overcome the orientation problem and fixation by airborne control for the location problem.

The surveyors had to improvise the way they performed their normal survey processes. All survey processes required the survey stations to have line of sight. The height of the vegetation in many areas was a problem (See Photo) and to overcome this, the survey station would be established on the top of an APC when available. Many schemes were conducted in this way saving hours of fieldwork. The observer had to be careful when setting up the theodolite and tellurometer to ensure they were stable. The real excitement came when observing a round of angles and it was necessary to move around on the top of the APC. On at least one occasion the observer, concentrating on his work, moved around the theodolite's stand and fell down the open hatch of the APC.

One noticeable aspect at the close of 1967 was the increase in mortar activity and the introduction of rockets to the local Province. Rocket Propelled Grenades (RPG), along with 60mm and 82mm Mortars were used in numerous attacks on villages and ARVN outposts. The Detachments Crater analysis team visited a number of these incidents; however, finding pristine craters for examination was very difficult due to the enthusiasm of the local population. In one particular case on arrival at one mortaring incident the ARVN soldiers handed the crater analysis team two half-filled sandbags of shrapnel and tail fins. In their efforts to help they had dug up all the craters, fragment identification confirmed the weapons used.

By late 1967 it was becoming necessary to find a solution to the problem of how to provide locating support to Nui Dat base and allow the deployment of both Radars to FSBs established to support operations. A decision was taken that the Det.131 should deploy a Sound Ranging Base at Nui Dat.

In mid January 1968, all task force units were withdrawn into the Nui Dat perimeter to prepare for Operation Coburg. The task force placed on alert during this period as a VC attack was probable.

Operation Coburg commenced on the 24 January 1968. It was the largest operation conducted so far by the Australian Task Force and involved three Infantry Battalions (2,3 and 7 RAR), and took place in the Bein Hoa province outside the normal Australian AO.

At Nui Dat at 2345 hrs on 31 January 1968, LPs 31A and 31D reported red flares in the southeast. This was the beginning of a long and hard year for the Det.131 although not known at the time the flares were the signal for the commencement of the TET offensive in the Province and heralded the commencement of a full-scale offensive throughout South Vietnam, with simultaneous attacks by the communists on five major cities, thirty-six provincial capitals, sixty-four district capitals, and numerous villages.

The flares also signaled the commencement of an estimated battalion sized attack on the provincial capital of Baria. The Task Force was placed on full alert and Alpha Radar was placed on a southern bearing based on reports from LPs. The Radar produced Locreps on three separate locations, however these locations were not fired on, air clearance had been given to helicopter gunships to over fly the area, and the location of friendly troops on the ground was not fully known.

During the remainder of the night there were numerous reports of incoming small arms fire although these reports were never confirmed. At first light a small relief column of Australian troops was sent into Baria to assist in "mopping up" operations, this small force was made up of personnel from a number of different Corps including a few Locators. Baria did not fall to the VC and by mid morning was back in control of the local forces.

During this period the Locators had their share of work with a mortar attack at Nui Dat on 1 Feb 1968 at 0300 hrs and three separate grenade attacks on the TF position. The enemy mortars fired approximately twenty rounds at the base, which did not breach the perimeter; 'A' Radar was quick to respond and produced Locreps, which were engaged within eight minutes by 105mm and US 8-inch guns. A patrol was sent to this position the following morning reporting a confirmed base plate site and that the enemy made a hasty retreat leaving behind twenty-five 82mm mortar bombs.

The three grenade attacks remained a mystery, on each occasion the detachments crater analysis team found fragments of M26 and one MK2 grenade, the grenades had landed in the same area on each occasion and at least 100 metres from any installation.

The bulk of the units on Operation Coburg were recalled to NUI DAT while a battalion continued the operation with a main base established at FSPB Anderson. Based at Anderson were B Battery 2/35 (US 155mm), 106 and 108 Bty (Aust.105mm) elements of Cavalry and a company of infantry as base defence. Also in position were Bravo Radar, an LP and a forward Arty Int. Office. This was a new trial system for the Det.13, 1 in that the Forward AIO would control the Radar and the LP in the FSB and would have the responsibility for all counter battery fire missions for that FSB. Part of the trial was establishing a landline connection between the three sections with only the FAIO in contact with the TFAIO (at Nui Dat) by radio.

At 0100hrs on 18/19 Feb 1968 the LP and US Bty reported a Red flare five hundred metres south of the base. This had hardly been acknowledged before the barrage of enemy mortars was heard. This first barrage cut straight through the centre of the FSB causing a number of casualties. A second barrage, which seemed to be adjusted, landed on the perimeter of the FSB, this fire straddled the LP (see photo. Lp at rear straddled by 4 Mortar craters) killing one LP Operator and wounding another A third barrage was fired, which overshot the FSB, however, while the Mortar attack was in progress a rocket attack commenced on the western sector, which contained the main elements of artillery, cavalry and engineers equipment. The US Bty also reported a ground attack on their position of some thirty to fifty Viet Cong. This attack was short lived lasting 10 to 15 minutes and did not cross the wire. (located about twenty-five metres in front of the guns.)

Bravo Radar produced a number of Locreps for a base plate positions, which were engaged by CB fire within 5 minutes of the first report. The base plate positions were engaged firstly with infantry mortars, then with the 105 mm and finally by 155mm. The enemy had fired approximately 40 to 45 mortar rounds of which some twenty five to thirty rounds fell inside the FSB, also fired were some sixty to eighty rounds of RPG, which landed inside the perimeter. Damage to equipment, Guns and vehicles was reported by US Arty, Cav and Engineer units.

An inspection of enemy base plate positions the following morning confirmed the Locreps to be accurate and within 25M of the actual base plate position. An unusual find occurred at the base plate position, charge bags for a 120mm mortar and a 120mm primer. This was unusual in that no 120mm mortars had been used against the Australian Forces. It is possible this weapon was fired at the base, however, even on minimum charge it would have flown well over the base.

FSPB Anderson was mortared for a second time on 28 Feb 1968 at 0100hrs. Again a red flare preceded the attack as the mortars were "walked" through the FSB, moving approximately one hundred metres with each barrage. As with the first mortaring, retaliation from the Radars and guns was quick with CB fire laid down on the target in less than 5 minutes. Between twenty- five and thirty rounds of 82mm mortar landed inside the perimeter of the FSB. The LP reported enemy movement directly in front at about one hundred metres. (The LP was using a US Starlight Scope, a light amplification system enabling the operator to improve the range and standard of night vision. Maximum range to identify an object at night was about 200 metres. This equipment was not available to the locators and had been 'borrowed' from the US Gun Bty.) There were at least twenty figures moving around and a request for an infantry mortar fire mission was granted (an earlier request to fire with small arms was denied), because of safety limitations the first rounds fell some three-hundred metres to the rear of this group. A second fire mission fell about one hundred metres to their rear and this started the group running. The US Gunners at this stage initiated small arms contact with this group and a firefight of about 5 -10 minutes ensued which also involved the LP when they received incoming small arms fire.

An inspection of the Locrep site was carried out at first light by an infantry section accompanied by two of the LP operators, they again proved the accuracy of the Locreps from the Radar. Many craters both mortar and shell covered the position indicating that targeting had been successful. With infantry as protection, the LP operators conducted a thorough search of the area. The following items were recovered:

" 32 x 82mm Nose Caps
" 3 x Chicom 82mm mortar bombs
" 3 x 82 mm fuses
" 2 x 120mm Chicom mortar bombs
In the tracks around the area were indications of a wheeled weapon, which could have been a 120mm mortar or a heavy machine gun. This weapon appeared to have been towed by three-wheeled vehicle. A second patrol visited the enemy movement and contact site and recovered an intact RPG7.

At FSPB Anderson, concern grew that the enemy was using the Radar as a target or control point to walk their mortars through the FSPB. An order came down for the Radar Section to construct a Radar 'look-a-like' and place it near the wire perimeter, alas the only building materials were star piquets, a 44-gallon drum, ration pack cartons and an off cut of a cam net. Picasso may have been proud of the result, but it failed to look like a Radar, especially when it rained and the cardboard dishes sagged towards the ground.

During OP Coburg, both Radars produced many Locreps not all were confirmed due to operation commitments. Apart from those already mentioned two other Locreps were confirmed as rocket sites for 122mm rockets. All units returned to Nui Dat on the afternoon of 1 Mar 1968.

At Nui Dat on 21 March 1968 at 2350 hours, 31A LP, a SAS bunker and a strong point of 161 (NZ) Fd Bty reported muzzle flashes from a mortar. Bravo Radar was immediately traversed to search a bearing sent in by 31A. A total of fifteen rounds were seen on the screen and a Locrep was produced. This suspected base plate position was never fired upon because a friendly patrol was located in the area and not in radio contact, but the patrol did confirm the next day that there had been mortars firing within four hundred meters of their position. Approximately twenty-five rounds had landed on or outside the TF perimeter.

21 April 1968 the Allied Operation "Thoan Thang" (Complete Victory ) commenced this would be the largest Operation conducted by Australia since World War II and would encompass all elements of the Field Force, and as with operation Coburg the major fighting elements of the Task Force were deployed in the Bien Hoa Province.

Det 131 supplied an FAIO, one radar and two LPs ,a total of 25 men or roughly a quarter of the detachment strength, this did not include the Survey Section who moved independently and supplied survey to all FSBs occupied .

The first three weeks of this operation were very mobile with the Radar and LPs deployed by air into three FSBs' Wattle, Mike and Anderson. After five days at Anderson, on the afternoon of the 12 May, the members were airlifted into FSPB Coral (see photo, FSPB Anderson 12 May 68)

FSPB Coral initially commenced with the securing of the area by a US infantry company and at the same time Det 131 Survey Sect. moved in by road to survey the area for the incoming Guns. The Surveyors found that the American troops were actually south west of the originally selected site. As the Survey party moved to the American position the fly-in of Australian troops began with the reconnaissance parties of 12 Fd Regt, 102 Fd Bty, 161 Fd Bty, and an advance party of 1 RAR who landed by midday 12 May 1968.

On arrival at the LZ (landing Zone) the reconnaissance party OC on being shown the results of the survey declared that it was the wrong area and decided to move to the surveyed area twelve hundred metres northeast. Unfortunately at this time 161 Fd Bty Guns were arriving by Chinook helicopter and requesting smoke to set the guns down. Although the situation was explained, the fly-in times could not be changed and the BK of 161 Fd Bty was forced to land his guns in this position. The remainder moved twelve hundred metres North East and commenced setting out FSPB Coral and awaited the fly-in of the main body.

12 Fd Regt HQ had dug their command post in with two feet of overhead cover and individual shell scrapes. 102 Fd Bty by last light had competed, by the use of unit bulldozer bunds for the three forward guns and a bund for the reserve ammunition.

1 RAR and 3 RAR after delays to the fly-in schedule were not concentrated at FSPB Coral till 1700hrs. Elements of 3 RAR were deployed back to the original LZ with 161 (NZ) Fd Bty. 1 RAR had expected to move to an area two thousand metres north of FSB Coral but instead, because of their late arrival, occupied defensive positions around Coral.

Alpha Radar occupied a position to the left of No.6 Gun of 102 Bty and the LP 31C was deployed on the right front flank of the Bty adjacent to 102 Bty M60 strong points. The FAIO was deployed with HQ 12 Fd Regt.

A one-metre deep shell scrape was dug by the side of the gun bund and the section Land Rover and generator were set up. The Radar command post was initially set up in an 11x11 tent until a mini -command post was dug and completed just before dusk, enabling the on duty crew to have minimal protection of two sandbags deep overhead cover. The mini-command post was extremely cramped only allowing for two persons side by side, with the computer and the CPI unit.

 LP 31E traveled by foot back some twelve hundred metres to where 161 Fd Bty had deployed, arriving there late afternoon.

At about 2400hrs on the night of 12/13 May 1968 LP 31C reported small arms fire and explosions approximately 3000 metres north of FSB Coral. This was later confirmed as a D Company 1 RAR ambush and the initial contact with the enemy. Five minutes later 3C reported small arms fire close to the gun position, this proved to be an enemy probe on 1RAR Mortar Platoon position.

At 0145 hrs the enemy launched a heavy RPG and mortar attack on FSPB Coral. Within minutes Alpha Radar ceased to operate, it was believed it had been hit with mortar or RPG shrapnel. It was later found that a number of the radar units and even cables had suffered shrapnel damage.

The enemy moved up behind this attacking fire to within fifty metres of FSPB Coral, from where they launched a battalion size ground attack which overran the mortar position and one gun of 102 Fd Bty within the first five minutes (See photo  102 Bty Gun 13 May 68)

LP 31C and 102 Bty M60 was also overrun and after a brief fight, contact was broken and the members were recalled to assist in defence of Bty HQ, the M60 machine gun was captured and dragged off by the enemy. This MG was later recovered by an infantry patrol two days later in scrub 300 metres from the FSB.

It would prove a long night for the FSPB and Alpha radar detachment had been sent to their shell scrapes and spent the night hunkered down while mortar rounds exploded, tracer and rockets filled the air. Having no pre-arranged defence plan it was obvious that it was unsafe to be above. A major concern emerged at this stage that if the VC moved their line of attack to the western side of the base there was absolutely no defence ie; Wire ,Claymores, defensive pits or Machine gun sites.

The LP at 161 BTY, alerted when the RPG and mortar attack commenced on FSPB Coral, immediately lowered their hootchies and as one gunner stated:

'We watched the massive RPG and mortar attack, we could see them quite clearly and where they fired from, then they began to airburst near us. The air was full of tracer and we could hear the sound of the splintex as it 'whooshed' out of 102 Bty Guns.'

Note: Because of the distance between 161 Bty and 'Coral' the 'air bursts', mentioned above, could account for the report that the NVA had tried to turn 1 RAR mortars back onto "coral' firing a number of rounds. At best they would certainly overshoot FSPB Coral

The LP could identify the rockets and mortars being fired from different location by the flashes but because of the noise and flares it became impossible to identify a location accurately. As their position was not attacked they could only sit and watch.

About 0800 hours a runner from 102 Bty came and collected the radar operators with orders to move to the mortar platoon position and assist in recovering the dead back to 102 Bty HQ area The wounded had been recovered earlier in the morning. The tent that was erected by the detachment the night before was used as an aide station. Once the Australian dead and wounded had been moved to a safe area, the Locators then joined the burial details collecting the remains of the enemy dead and transporting them to a communal burial site and assisting in recovery of equipment from the 1 RAR Mortar position.

LP 31E returned by foot from 161 Bty and was surprised by the amount of equipment that was scattered around. Before they could set up they were immediately placed on the burial detail for the enemy dead and general clean up of the area.

( see photo, LP member at 1 RAR mortar position )By mid afternoon the members of LP 31E were airlifted to FSPB Coogee a base established by 3 RAR into which 161 Fd Bty moved.

An early morning inspection of the Radar and its ancillary equipment found that the Landrover and generator were extensively damaged by rocket and small arms fire and were completely unserviceable, the radar also carried shrapnel and small arms damage urgent replacement for these items were requested from Nui Dat

On 13 May 1968 at about 1145 am the first of two Task Force Maintenance Area (TFMA) road convoys from Nui Dat arrived. With the convoy were two vehicles from Det 131 carrying replacement members and replacement parts for the damaged radar and defence stores Members returning to unit

Selection of a new site for the radar began immediately. The new site was completely unsatisfactory to the radar personnel. After stating that locating mortars from a technically unsound position would be difficult, the command post was completed with the assistance of TFMA bulldozer.

At 0230 hours 16 May 1968, the enemy commenced a heavy mortar and RPG attack directed mainly at A Company I RAR and the Task Force Headquarters area. At 0240 hours, under the cover of this supporting fire, the enemy attacked A Company and B Company, 1 RAR, in battalion strength. Although the enemy occupied some of the forward pits of A Company, the attack was held on the perimeter. The enemy broke contact at approximately 0340 hours. Throughout the night the enemy continued to assault other parts of the perimeter. At 0515 hours, the enemy attempted to thrust between A Company and C Company through the Assault Pioneer Platoon, but this attack was prevented by mortar fire, claymore mines and small arms fire. An attack was then mounted against all three companies, but this was also repulsed.

Alpha radar received no search bearing from AIO and did its own continuous search of suspect areas although lock-on was achieved on many signals no successful location was achieved. Although the Radar Antenna received a number of shrapnel and bullet holes the Radar continued to function.

The LPs continued sending in many Mortreps and AIO acted upon these to conduct CB fire using Mortars as the attack was close to the FSPB.

During the attack the TFAIO sent target information to the mortars and guns. 1 RAR Mortar Platoon is reported as firing about 750 rounds from four mortars. Two mortars were mounted in APCs and two were on the ground. Many of these were in response to TFAIO requests.

At approximately 0645 hours, the enemy finally broke contact and withdrew. Their confusion was apparent from the air, and they were engaged by artillery and a number of tactical air strikes. Due to the fire support and air activity neither cavalry nor infantry were deployed to pursue and harass the enemy until 0815 hours. On 17 May 1968, 1 RAR patrols located mortar base plate positions used during the night 15/16 May, and they also found quantities of ammunition. The enemy position had been heavily hit by 1 RAR mortars employed in the counter mortar fire role.

FSPB CORAL (See photo FSPB Coral 26 May 68) received mortar, 75 mm RR and RPG fire from 0415 hours to 0430 hours on 28 May 1968. This was the last enemy attack on CORAL, and coincided with a battalion-sized assault on FSPB BALMORAL.

Alpha Radar was ordered on to a search bearing to support BALMORAL and recorded three separate mortar locations and sent the Locreps to the AIO. 102 Fd Bty fired on all three Locreps. Results of this engagement were not known. FSPB BALMORAL was abandoned on 5 June 1968, and FSPB CORAL was abandoned on 6 June 1968, both without incident.

A Sound Ranging base was employed at Nui Dat and enjoyed a number of successes in locating enemy mortars and rockets. On the two occasions Nui Dat was rocketed and mortared in 1969, the Sound Ranging base located both launch sites and base plate locations, which were confirmed by ground patrols. The second attack occurred during the battle of Binh Ba. Three 107mm rockets were fired at the 1 ATF base, exactly one hour later three more fired. Both firings were located and it was determined the launch sites had been pre-set and timers used.

When the attack commenced, activity around the base increased, especially the helicopters, which caused enormous interference to the Sound Ranging microphones. This was reported to Task Force headquarters and the Task Force Commander ordered the helicopters out of the area, this action displayed the respect the sound ranging data had achieved. On another occasion, an infantry patrol became lost and the Sound Ranging base was called upon to find them. The patrol tossed a grenade and soon they were on their way home.

During the deployment of FSB Polly in July 1969 Det 131 Survey were working on a survey scheme when the driver of the bulldozer clearing the perimeter cried out 'Oh hell' (or words to that effect). He had scooped up a command-detonating mine. The mine consisted of 5 mortar bombs tied around explosives from which cable ran into the trees nearby. It appeared the driver had cut the cable as he turned up the mine. The mine was located only 10metres from the site where the surveyors were working.

Det. 131 was selected to conduct trials on the then highly secret equipment called sensors. Although not used strictly for Artillery Intelligence, Det 131 was chosen because it had a command structure and a radio net that went straight to the Task Force headquarters and had personnel familiar with surveillance duties and a workshop capable of maintaining the equipment. Because of the secrecy of the new equipment, the code name 'Duffle Bag' was used when referring to this equipment

Training was conducted by the US at their sensor training school at Vung Tau. There were several types of sensors available.

" Seismic - detected movement in the ground;
" Magnetic - detected metal moving through its field;
" Acoustic - detected sound
" Thermal - detected heat (based on human body heat)
The sensors could be several kilometres from the base station and the data was sent by radio link, so line of sight was essential. Normally a string of sensors were set along a suspected enemy route. The string would consist of a variety of sensors to assist in eliminating false readings: For example, wind blowing a tree or an animal would cause ground movement and activate the seismic sensor, but it was improbable for that tree or animal to be carrying metal and therefore activate the magnetic sensor.

The string would also be laid to allow the direction and speed of movement to be determined. It was normal Australian operating procedure to deploy a string to listen in and gain intelligence. From the information gained a decision was made at Task Force headquarters on what course of action was to be taken. Several large and successful ambushes were set as a result of intelligence gained from sensors.

It was vital to the success of each sensor operation that the sensor-string be placed in position unseen by the enemy and with minimal disturbance to the area. To do this a sensor team supported by SAS or D and E protection party would quietly move into the area of interest and install the devices. No evidence of having been in the area was left and the sensors were virtually invisible to the eye as the aerials were manufactured to give the appearance of grass. To deprive the enemy of information about the equipment each device self-destructed if tampered with. If a device were located by the enemy they would avoid the area.

The secrecy surrounding the program caused some problems as is demonstrated in this quote attributed to the OIC of the Sensor Team:

'On a number of occasions, the monitor stations could hear Australian Infantry and engineers as they examined a sensor transmitter station, more than once they heard "I dunno what it is, so let's blow it".( see photo) And blow it they did, before monitoring personnel could take any action to prevent the destruction of the painstaking work on their part and the SAS and D and E Platoon'.

The sensor program concluded when the Task Force was withdrawn from South Vietnam late in 1971. In all the Australians deployed thirty-three sensor strings. Monitor stations were located at Horseshoe Feature and Nui Dat Hill.

On 4 February 1971 the survey section moved north by road convoy with the Regiment to establish a FSB. The landrovers of the section were immediately behind the three Centurion tanks that were escorting the convoy. The driver of the first survey vehicle followed the tank tracks as best he could. He had his driver side wheels in the right hand track marks of the tanks. As they approached a corner of the road the passenger side wheel ran over a mine.

The vehicle was badly damaged by the blast and a fire, which was started by trip flares carried in the vehicle. It was not worth recovering and with the aid of the engineers was buried at the spot. suffered shrapnel wounds and bruising and were medivaced back to Australia in early February1971. The other two suffered minor wounds and perforated ear drums but remained in Vietnam. Written off with the vehicle were all the stores that it had carried and rumour has it, that every deficiency in the unit Q store was in the vehicle at the time of the fire.

On 5 June 1971 the survey section was to undertake one of its largest commitments. Operation Overlord, a three battalion operation to cordon and search an area in the north of Phouc Tuy province. The artillery plan involved the establishment of three new FSB Pamela (A Field Battery), FSB Trish (104 Field Battery) and FSB Cherie ('C' Battery, 5 Battalion 42nd (US) Artillery). An important ingredient for the success of the operation was surprise. To achieve this, the forces involved were to be inserted simultaneously.

To achieve the survey at each FSB on time it was necessary to conduct a visual reconnaissance of the area but to do so could compromise the whole operation. Special permission was received from the Task Force commander to over fly the area in a helicopter. It was made abundantly clear that the flight was not to compromise the operation. A Bell Sioux piloted by the 2 ic of 161 Squadron, departed Nui Dat at lunch time on 4 June with the survey section sergeant aboard. It was explained to the pilot the concerns of compromising the coming operation and also the critical need to be able to look at the country from the lowest possible height so that line of sight could be determined.

For the next hour, what must have seemed like the greatest joy flight to any one watching the helicopter as it flew over several areas much of it at very low level. The skids on the helicopter almost cutting grooves in the ground. Upon return, the survey plan was drawn up and orders prepared. Next morning the section deployed to the area and provided the three FSB with theatre grid and orientation. It was a credit to all the section and the skills of the pilot the previous day. Interestingly, during the day when giving one of the battery's their survey data, the Commanding Officer of the battalion and his RSM were encountered. They argued that the grid we had given the battery was wrong. They had conducted a map spot and regardless of any explanation they were given about how accurate our work was they would not be swayed. In the end we decided it was useless to push our point further, smiled a farewell to the Battalion CO, gave the battery our results and moved on.

It is hoped that this may give the reader a small idea of the workings of Detachment 131 Divisional Locating Bty (SVN). The Dragon and locating Atom are official emblems of Det 131 and the current Locating unit 131 Surveillance and Target Acquisition Battery

The above article is copyright to Keith Ayliffe/ John Posener and Australian Military History Publications. Ern Marshal is Authorised to use Part or All of this article.

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