Pillboxes and Howitzers

Early 1942 - Pillboxes and Howitzers to defend against land assault

The gun battery commanders had every confidence in their ability to defend themselves against ships but what they were most afraid of was a direct enemy infantry attack on the island via landing craft.

To combat this threat, the army created infantry defences using a short range howitzer battery to defend the big guns. The small three gun battery was intended to defend the island against direct assault. The howitzers were light enough to lug around on the back of a couple of old Bren carriers. They could fire a 9kg shell about 6km.

The Pillboxes

In 1941 when Japan entered the war, a decision was made to build 16 pillboxes to guard the battery and adjacent gullies up which the enemy might approach.

They had heavy and light machine guns, rifles and 3 inch mortars at the ready. Besides the pillbox at the top of Northern Junction, you can see three more embedded in the sides of the gully heading down to Mullet Bay and there is also one hidden right in the corner of the beach. In paddock 14 there is another right in the middle of our plantings. They had wooden sleeping benches, softboard linings and were in telephone communication with the battery. Two men slept while the third kept watch.

Trustees and volunteers have located and examined all 16 pillboxes. Some are in seldom visited areas of the island whilst others are in fairly steep and/or relatively well concealed locations. The Department of Conservation have surveyed and tagged all these structures. Earth works prohibit entry through the rear access doors. Some of the furnishings in these pillboxes remain in place and are in a remarkable state of preservation after 67 years.

Two more camps, the Infantry camp and the Howitzer camp, were constructed to house the additional troops. They were built along the sides of a gully off which the underground plotting room complex had been built.

The Infantry Camp

Because of the urgency to get troops onto the island, normal barracks were not built. They initially pitched tents then 30 dugouts with earth floors, wooden walls and roofs were built. The dugouts were excavated into the side of a bank. After the timber flooring and roofing was completed, topsoil was placed over the roof. Nine prefabs were erected for mess rooms, cooking, ablutions and toilets.

You can still see remnants of foundations. Other traces include concrete foundations for the cook house and toilets. The dugouts themselves have been filled in but the site of the buildings and dugouts is quite noticeable with the scarping to accommodate them being very prominent

The Howitzer Camp

howitzer camp

The Howitzer Camp was located along from the Infantry Camp across the road from where the Rotary Centennial Track emerges at Northern Junction. In the drawing you can see the relationship between this camp, the infantory camp and the above and below ground plotting room complexes.

The small three gun battery was intended to defend the island against direct assault. There were a total of 8 timber buildings constructed for cooking, washing, and toilet and mess facilities for the men. Accommodation was again provided in the form of dugouts. Six structures were excavated into the side of a bank, floored, walled and roofed with timber, topsoil paced over the roof. Number 37 on the drawing is the cookhouse, the remains of the fireplace can be seen in the distance in this pic.

howitzer camp showing the scarping

A concrete foundation slab for the toilets and the remains of a fireplace, possibly part of the cookhouse, are the only tangible reminders remaining. The site of the buildings and dugouts is noticeable with the scarping to accommodate them very prominent. It is the first military site that can be viewed when you leave the track to head up the road to the pillbox and interpretative panel

Late 1943

By late 1943 with the threat of attack greatly reduced, the troops and artillery were withdrawn and the two temporary camps abandoned. In 1945-46 both camps were demolished and the prefab buildings were removed by the War Assets Realisation Board.

US Navy Magazines

US Navy Magazines

50 large prefabricated concrete underground storage sheds (magazines) were completed at the south western end of Motutapu by the US Navy in 1942

us navy magazines
US navy magazines and connecting roads under construction early 1943

In that year, the United States decided that Auckland Harbor would become the US Southern Pacific fleet operating base.

This resulted in a massive military build up of troops, ships and aircraft into the area.

A huge base was to be built at Yankee wharf on Rangitoto and Motutapu was to become the main storage bunker location for munitions.

The entire defense structure of the area had to be upgraded to protect The US Pacific Fleet which was going to anchor between Tiri and Rangitoto within the gun and mine defences of the port.

b motutapu and rangitoto are joined by a short causeway
Gardiner Gap today. The outlines of the roads and magazine sites clearly visible

In late 1942, 50 large underground magazines were constructed by the US Navy and 40 other buildings were built to support the magazines. The facilities were completed in July 1943
The magazines were built recessed into alcoves cut into the undulating hillsides.
Precast concrete sections were assembled on top of a poured concrete slab. Each magazine measured 24 x 6 metres.
After assembly, earth was piled up over their sides and roof only leaving the front side uncovered.
The US Navy already had 15 ammunition magazine storage facilites at Kauri Point Birkenhead but they were never going to be sufficient to support the fleet.
The support buildings included a massive US Navy warehouse store at Home Bay (3000m2 and 110 mtrs in length). The concrete foundations can still be seen behind the camp ground toilets. The building was removed by RNZArmyEngineers in 1970 in what was their biggest peacetime task ever attempted at that time. 61 engineers carefully numbered and dismantled the building then shipped everything to Papakura Military camp where the store was reassembled to house army vehicles.
11 km of access roads were built (including the Causeway) linking the magazines to wharf access at Rangitoto (Yankee Wharf).
The entire complex cost $13.6million (2008 dollars) - the US Navy Fleet never came and the magazines were never used. The war had moved quickly north in 1943.
The US Navy handed them over to the New Zealand Army who blew a few up for demolition practise. You can still see the ones they blew up over by the Motutapu Restoration Trust nursery including this example pictured below.

target practise

The 'Bunkers' post war and today

After the war, in the early 1950s, the magazines were used to store wool by the New Zealand Wool Board and for the storage of farm equipment. They are mostly all still there and many remain in reasonably good shape after almost 70 years.
The farm and the Department of Conservation continues to use some of the 'bunkers' for materials storage.

Many of the magazines are only now starting to deteriorate at a rapid rate. The steel reinforcing rods are rusting out and 'exploding' the surrounding concrete.
bunker interior 2

bunker interior

They are much easier to spot in summer when their grassed earth camouflage cover dries out and the grass browns off.

two bunkers

underground bunker sign

Underground Magazines

Adjacent to each gun and approximately 8 metres below ground, a magazine was constructed to store both shell and cartridges for the guns

underground magazine

The magazines are accessed by a set of stairs leading from ground level and opening into a short corridor.

Nearby a vertical shaft provides ventilation to the magazine, it is also equipped with a ladder to enable it to be used as an emergency exit.
The magazines are of massive construction with walls 600mm thick.
Ammunition was lowered down into the magazine by means of a davit positioned in one corner of the stairwell. This pic shows the number 3 magazine Shell Store. Note the surviving metal rack framing and the lighting fixtures. The shell hoist up to the emplacement above is at the far end of the Store.

The Burster Slab

The construction of the 'Burster Slab' is impressive, a layered type of construction forming the roof of the magazine.
Targets were expected to engage the battery from long range meaning shells would be falling vertically onto the battery (rather than striking the battery horizontally from shorter range). Targets would be described as Destroyers or Cruisers firing 8 inch guns from 25 to 30 kms out in the Gulf.
The magazines needed to be protected from this plunging fire.
They were built recessed into the ground using the usual cut and fill method of construction and protection from the plunging fire was provided by the 'Burster Slab'
the underground magazine number 3

The Burster Slab layers described

underground armour plant roof

Refer the design drawing above. Folded steel armour plate froms the immediate ceiling of the magazine (folded or corrugated steel provided the necessary strength). This pic shows the ceiling in the Number 3 Shell Store.
The armoured plate is covered by a poured slab of concrete nearly 1 meter thick.
This in turn is covered by 900mm of sand (taken from Pig Bay, the next bay south of Administration Bay).
This is then covered by another slab of concrete 750mm thick - these three layers - concrete then sand then the second layer of concrete - effectively constitutes the 'burster slab' designed to resist the impact of incoming shells falling on the battery/magazines vertically. A second layer of 900mm of sand is laid over the burster slab. A final layer of 0.6 metres of earth completes the installation.

Inside the Magazine
The Magazine Layout

The three magazines measure 12 x 8 metres from floor to ceiling
A central wall divides the space into a shell and cartridge store. The first room you step into is the shell casing room or shell store, the room adjacent/behind is where the cartidges were stored. The dividing wall is constructed of brick.
The shell store is lined with a second skin of brickwork, presumably also in an effort to maintain constant temp/humidity conditions within (see 'Humidity Corridor' below)
Each of these rooms was previously outfitted with shelving and racks to store the munitions. There is remnant racking along the central wall of the shell store. This is the steel framing upon which the shelving timber planking was constructed.
Many of the light fittings still remain in place
The folded/corrugated steel armour plate roof is still in reasonable condition
The number 1 and 2 underground magazines still have the steel blast doors at the entrance to the shell room.
Number 1 has a fitted wooden bench still in position outside the entrance to the shell room.
Unfortunately all Cartridge Rooms show evidence of vandalisation where attempts have been made (some successful) to chip away brickwork to remove solid brass fittings.
The Shell Hoist

At the end of each magazine closest to the emplacement and leading up to it at an angle was a hand operated hoist. This supplied both shell and cartridge to the working area
It was in the form of a rectangular metal shaft containing a rotating dredger-like hoist within.
At each end of the hoist aperture was a series of doors controlled by interlocks to prevent the flash from an explosion passing down to the magazine. If one of the doors was opened, the other would automatically shut.
The hoist was hand powered
There is also a vertical shaft ventilation/escape route with an 8 metre steel fitted ladder leading to outside.
Humidity Corridor

Around the magazine runs a small tunnel or Dry Area.
This construction was intended to keep the temperature and humidity constant within the magazine as variations could affect the performance of the ammunition


Underground Plotting Rooms

Visitors are requested to enter the Underground Plotting Rooms Complex only in the company of either DoC staff or Motutapu Restoration Trust volunteers. There are health and safety issues underground that remain to be resolved.

A decision was made by NZ Defence Chiefs in early 1941 to relocate the Plotting Rooms, radio room and engine room underground. These were the key targeting, communication and support services for the gun battery. The facilities were located on a ridge alongside the Miniature Range and so, easily exposed in the event of an attack.

The project took almost 12 months to dig out and build. Work began in August 1941 and completed in July 1942. This was a significant piece of engineering and involved the excavation of 28670 cu yards of material (22000cu metres) and the pouring of 647 cu yards (500 cu metres) of concrete. Total cost was 15,617 Pounds ($1.2m in 2008 dollars). The complex consists of a series of rooms completely surrounded by a humidity corridor having the same ceiling height. Steel shuttered windows open out from the rooms into the corridor.

Top Tunnel

The top tunnel is 37 mtres long. The radio/wireless room is located on the left hand side soon after entering the tunnel. Large ventilation pipes are set along the right hand side wall. At the end of the tunnel, the water tank to cool the diesel generator is still largely intact. In wet weather there is some seepage through the roof of the tunnel resulting in water pooling outside the Engine Room.

Wireless Room

The radio/wireless room is 13 feet by 10 feet (4 x 3 metres)
The room has a humidity control corridor surrounding the room similar to the corridors surrounding the gun emplacement underground magazines. In this example, however, the ceiling height is consistent with the wireless Room itself. Steel shuttered windows open out into the corridor. Joinery, softboard wall coverings, and piped services gear is still in evidence.

Engine Room/ Fuel and Battery rooms

The purpose of this room can be easily recognised by the raised plinths on the floor upon which the generators were sited
The engine room is 20feet by 19feet (6 x 6metres)
The small room to the left hand side was the fuel store and the small room directly behind that was the battery room.

The Plotting Rooms

The two Plotting Rooms handled the fire control equipment and are described in more detail below. Underground transmission cables moved data around between the fortress plotting room, battery plotting room, observation posts and the gun emplacements themselves. Some of these transmission cables can still be seen where they terminate.

Battery Plotting Room

Next room moving left down the corridor is the Battery Plotting Room (has the cupboard in the right hand corner).
The Battery Plotting Room and the Fortress Plotting Room combined were 38 feet long by 19 feet wide (12 x 6 metres)
Up to 15 people worked in this area (3 telephonists, 1 talking to the Fortress plotting room, 1 to the fire command post etc...6 people operating the Fire Direction table, 2 the coordinates converter, others monitoring the time of flight indicator, the ballistic correction calculator, depression rangefinders, range transmitters, range and bearing dials and rotary converters)
Data was passed to the Battery Plotting Room from the Fortress Plotting Room.

Fortress Plotting Room/Command Exchange

Next room still moving left is the Fortress Plotting Room, slightly smaller than the Battery plotting room.
The small room in the front left hand corner of the Fortress Plotting Room was the command exchange (where all the incoming and outgoing phone communications were handled)
The Fortress Plotting Room received inputs from the Auckland Fortress Area which included Motutapu, Rakino, Rangitoto, North Shore over to Green Bay, Otahuhu Isthmus to Tamaki Heads
Around 9 people would have operated in this room, 6 working on the plotter, 2 telephone/exchange operators and 1 encoder

Lower Tunnel

The lower tunnel is considerably longer at 60 metres with a toilet located inside the entrance (urinal and cubical in reasonable condition). The tunnels drains have been blocked and the water table has risen since 1942. This has resulting in this tunnel remaining flooded for a considerable number of years and prohibiting access.

Recent Developments - drainage initiatives

Recent earthworks by contractors employed by DoC have included the removal of a large quantity of soil adjacent to the tunnel entrances and the installation of a larger culvert by Home Bay road to assist drainage. This lowering and remodelling of the landscape has been successful in allowing water to drain from the tunnel. The mud left behind in the lower tunnel has yet to be removed

The underground complex is a replica of the above ground structure (has the sod growing on the roof). The above ground building is now in a poor state having been used by sheltering stock over many years. The Fortress Plotting room is the larger room with the command exchange cubicle still evident. The building with the pitched roof located alongside is the Miniature Range and is of considerable interest. BothThese buildings were constructed in 1937.

The Miniature Range

This building was partitioned into several spaces to incorporate a main plotting display, several sighting booths, telephone exchange and control room. No trace of any internal partitioning or equipment remains.

The Miniature Range was an early 'simulator'. There were only two ever built in New Zealand to support a gun battery. The other was at Godley Head near Lyttleton.

The main plotting display room was taken up with a large scale model depicting the islands and the Hauraki Gulf area within the guns field of fire. Gunnery officers practised the fall of shot on a target. Each shell strike was indicated by a peg pushed around a model ship. The Officer called his estimated correction. Calculations based upon his correction call were made and a peg thrust up to mark the corrected strike. Subsequent corrections were called until such time as the peg arose under the model ship indicating he was on target.



Battery Observation Post Complex

Battery Observation Post and Radar Room (Radio room obscured)

At Northern Junction, passing through the farm gate to the (Left hand side of the interpretative panel) you are now moving towards the gun battery. To the south east (Right hand side - across in the adjacent paddock) you can see the collection of structures forming the Battery Observation Post (BOP) complex.

These structures include : 

 - Battery Observation Post (grass covered turf on roof)
 - Radar Room and Radio Room (adjoining)
 - Above ground Wireless Room
 - Emu Observation Post

Plus their associated Engine Rooms. All these structures are included in a Restoration Plan drafted in 2001.

Above Ground Wireless Room

The first structure you see on the right hand side is the Above Ground Wireless Room built in 1937. The bulk of the building is constructed below ground with only 750mm standing above ground. The building can be accessed from either end by a set of stairs. The 'room' consists of three rooms (1 large and 2 small).

There is a good view from here down into Mullet Bay. The plantings on the slope to the left of the beach were carried out by Downtown Rotary. The planted pohutukawa on the right hand slope were part of the Project Crimson project and were planted in 1994/95.

Battery Observation Post (BOP) - Radio Room - Radar Room


battery observation post

Also completed in 1937 and partly recessed into the ground, the Battery Observation Post provides a 220 degree field of view.

 The radar room was built adjacent to the BOP and to the rear is a radio room. The area between these three spaces was in filled to provide an access lobby.

The doors were made of steel plate with steel windows and shutters. The BOP housed all the range finding equipment

There are plinths used for mounting equipment upon. There is also a network of open channel floor drains and piped services can still be seen extending from the radio room to the radar room. The radio room (the smallest room) features the remains of radio switching gear mounted on the west wall.


There are depressions in the ground nearby (slightly downhill from the structures heading east).

They were earth dugouts (shrapnel pits) with timber roofs overlaid with turf built for the safety of personnel.

There is an excellent view to be had from here across to the gun emplacements.

The picture on the interpretative panel at the Northern Junction showing the Battery Commander and the last test firing of the guns in 1957 was taken just outside the Battery Observation Post.

Emu Observation Post (EOP)

This was the naval anti submarine observation post manned by Navy personnel. It was used in the detection of enemy ships and submarines by monitoring the indicator loops and ASDIC arrays laid underwater out in the Gulf. Its other role was observation of the contact minefield.

Again partly recessed into the ground and accessed by a set of stairs. It had its own power supply, fuel store and rest room. It is subdivided into a number of rooms to allow the operation of all the various equipment. It is difficult to see this structure from the track to the emplacements; the EOP is located downhill from the two farm water tanks.


Both the EOP and the BOP had their own engine rooms where power was generated.

Their interiors are divided into two rooms - the larger is the generator room, the second is the fuel store.

The Emu engine room is partly recessed into the ground and accessed by a set of stairs; they were diesel generators with armoured cables in shallow trenches taking the electricity to where it was needed

WWII Military Timeline

Motutapu 6inch Mk21 Gun Battery

75 year Time Line - 1933 to Present Day






Construction authorised as part of a 6 year NZ army modernisation programme



Sites investigated. Red Bluff near Milford (NZ choice) was deemed unsuitable by the War Office as Counter Bombardment Batteries needed to be built well in advance of the object they are required to defend. War office suggests Rangitoto. Agreed on Motutapu as a 6inch 45degree battery would provide complete defense against bombardment by 8 inch cruisers operating between Tiri and the Noises (their extreme range)





Relief workers clear battery and barracks site of scrub







Contract let for construction of gun emplacements and associated buildings to Brays Construction under Public Works Department supervision
Road access from Home Bay to site completed



Majority of construction equipment arrives on site
Excavation work commences
Road constructed to Pig Bay to obtain sand for the construction of hte underground magazines



First two gun barrels and associated equipment delivered
Quarry was begun at Home Bay to supply road metal



Work well advanced on two magazines
Work began on the Home Bay wharf, Public Works camp set up at Home Bay to accommodate workers



All three magazines and burster slabs completed





All three emplacements excavated
Road constructed to Pig Bay to obtain sand for construction of the underground magazines



Emplacements construction complete
Battery Observation post completed
Command Post, engine, radio and plotting rooms complete.
Observation and Fire Commander's posts completed at Matiatia and RangitotoAdministration Bay barracks site drained, watercourses alteredWorkers camp established
Watch room behind the battery completed



3rd gun barrel delivered together with associated equipment
Emplacements completed and grassed



Constuction of barracks at Administration Bay commences



Army begins installation of armaments



Guns shipped to Home Bay and trucked to the emplacements
Gun 1 mounted



Guns 2 and 3 mounted
Magazines interior fitout complete
Administration Bay admin block, guardroom, mess and storerooms completed and handed over to the army
Gun test firings commence



Army HQ Wgtn advised that 'proofing' of the Battery carried out by Northern Military District Commander on 9th Sept. Battery is ready.


Top secret radar experiments (shore to sea, shore to air radar tracking systems) comence under Sir Ernest Marsden (had spit the atom earlier with Rutherford). Activites are housed alongside the Battery Observation Post. Was called the 'HS and C' (Hightly Secret and Confidential)



Allies declare war on Germany, 3 September, following German invasion of Poland
Population on Island increases from 10 to 200 overnight


Financial approval for final outfitting of Battery camp and the outlaying observation post camps
Rugby matches played at 'Dutchy' Looman's sheep paddock at Home Bay



German raider Orion sinks the steamer Turakina off Cape Egmont



Germany, Italy and Japan sign pact



Battery Camp complete
6 barrack buildings, officers quarters, dining rooms, rec rooms, hospital etc.. capable of accomodating 300 men completed
Construction of smaller camps at observation posts completed



German raiders sink Holmwood (off Chatham Islands) and Rangitane (off East Cape)



All married men in unreserved occupations called up for military service



Decision made to relocate Plotting room, radio and engine rooms underground - work commences
Searchlights authorised for emplacement at Billy Goat Point (to illiminate vessels attempting nighttime apporach)



Japan attacks Pearl Harbour 7 December
Britain surrenders Hong Kong to Japanese, 25 December
NZ 'ers have first contact with enemy (67 squadron RAF) during Japanese raid on Rangoon



Fearing land assault, short range howitzer battery arrive on island (three 3.7 inch howitzers WWI guns). Howitzers located on hill behind battery - ability to fire on main landing beaches.
Barbed wire laid along all main landing beaches
Ring of 17 pillboxes built to guard battery and adjacent gulleys



Singapore surrenders to Japanese
First enemy air raids on Darwin (total of 64 raids between Feb 1942 and Nov 1943)
Temp Infantry camp built near the underground complex under construction



13 Mar, seaplane from Japanese submarine I25 overflies Auckland photographing defenses at dawn.
Road from Islington Bay to Administration Bay completed by Fletcher Construction for the army
Light and medium anti-aircraft guns (Oerkilons and Bofors) positioned on ridges around the guns
Light Lewis machine guns mounted on roof of Command Post and the Battery Observation Post


US Admiral Nimitz assumes responsibility for South Pacific (including New Zealand)


US Navy identifies Auckland as a major US Navy base. Fleet anchorage between Tiri and Rangitoto.
Plans drawn up to create appropriate support facilites.
Construction commences



NZ prepares for possible invasion - City evacuation plans prepared 
Construction of the Controlled Mine Base at Islington Bay, Rangitoto commences (completed - May 1943)



Japanese forces heading for Port Moresby suffer setback in battle of The Coral Sea, 8 May
24 May, seaplane from Japanese submarine I21 overflies Auckland's defenses, again at dawn (believe this is the floatplane seen by Major Derek Thorburn and reported to North Head, they told him ' not to worry as its not one of ours'.)


Japanese Midget subs attack Sydney Harbour, 31 May (Group of submarines assembled offSydney commanded by Commander Imada Hiroshi, from the same submarine 121)



US victory at Battle of Midway effectively ends any danger of NZ invasion



Underground facilites and tunnels completed



Air raid drills being held regularly in NZ schools
Allies land offensive at Guadalcanal



US Navy identifies Auckland as a major US Navy base



Billy Goat searchlights (2) plus directing station, power supply and crew accommodation completed (to minimal design) to counter midget submarine, torpedo boats entering the harbour.



Japan commence withdrawing forces from Gauadalcanal



USNavy completes construction of 50 large concrete underground magazines (24mtrs x 6mtrs) at south western end of island liked by 11km of new road.
Camp for US Marines to sevice the magazines built on northern side of the road above the current rangers house at Islington Bay
Large support storage facility at Home Bay completed and later used for some time by the NZ Army (removed in 1950's and relocated to Papakura Military Camp - concrete floor still obvious next to camp toilet block). 
9km of link roads plus a wharf (Yankee Wharf) at Islington Bay and a causeway linking the two islands (the fleet never came and the magazines were never used)



Allied and US troops retake Georgia and Solomon Islands
Threat of attack on New Zealand recedes, Motutapu assumes more relaxed atmosphere. Planned additonal defence projects halted



Australians capture Lae, New Guinea and attack Japanese ships in Singapore



3 NZ Division secures Vella Lavella



Risk of attack dimishes, War in the Pacific has moved north
Troops and artillery withdrawn and temp camp abandoned



Battery placed in reserve (guns manned only at dawn/dusk - 1 gun could be fired within 10 mins, Gun 2 and 3 within 30 mins)


RNZN establishes Anti Submarine Fixed Defense Station ("Emu") in front of the Battery Observation Post to listen for subs and ships
Radar fire control installed rendering Fortress System obsolete (ability to plot both range and bearing day and night). Observation Posts abandoned



Dawn/dusk manning discontinued
D Day - Allied landing in Normandy



Gen MacArthur returns to Phillipines
Army engineers remove barbed wire from coast.
Dismantle buildings at all camps exept the Mine Base, HMNZS Emu and the artillery camp at Administration Bay
Only 50 people remain at artillery camp, mainly staff and service crew for the radar units



Allied planes bomb Singapore and B-29's bombTokyo



German submarine U 862 cruises into Gisborne and Napier ports looking for suitable vessels to attack (didn't find anything worthwhile but got close enough to watch couples dancing in the street cafes)



US flag raised over Iwo Jima



British liberate Rangoon, Burma



US troops liberate Phillipines



US drops bomb on Hiroshima 6th Aug, Nagasaki 9th Aug


Germany surrenders on 8 August



Japanese surrenders unconditionally on 2 September aboard the USS Missouri




Battery now only used for training
Both Whangaparoa and Motutapu now termed 'Port Approaches Batteries'. Both using fire control radar - greatly extending their range and effectiveness
Restrictions on public access lifted except for the camp areas
Remaining W.A.A.C's and service crews leave the island
Administration Bay camp begins use by territorials as part of the Compulsory Military Training (CMT). Continues through the late 1940's and 1950's.



Battery closed and placed in reserve
Long range fire responsibilities now assumed by the 9.2inch battery at Whangaparoa



Whangaparoa Battery laid up
Long Range responsibilities again assumed by Motutapu
Training recommences



Personnel withdrawals commence heralding the end of NZ's coastal artillery
Live firing exercises continue



Coast Artillery disbanded following Defense Force review (in common with Aust, Canada and Britain)
Motutapu battery now laid up. Recognition fixed coastal defences no longer part of modern military thinking



Battery area stripped of any salvageable material - only the guns remain



Guns offered for sale




Successful purchaser, Bradmand and Co, cuts up the guns for scrap
Army uses Administration Bay camp for training and storage
Administration Camp now empty (due to the decline of CMT, easing of Cold War tensions)



Administration Bay facilities begin operating as an outdoor education camp



Army vests all the battery land under the control of the Hauraki Gulf Maritime Park Board


Park Board re-establishes an outdoor education camp at the barracks area of Administration Bay


The Battery land later passes to the Department of Conservation



The Motutapu Outdoor Education Trust is formed and assumes the lease from DOC



The Administration Bay complex continues to be managed by the Outdoor Education Trust (MOEC) offering a huge range of activities to thousands of Auckland's kids annually.

Special thanks to Peter D Corbett's 'A First Class Defended Port' Department of Conservation, published July 2003, Motutapu Restoration Trust's Chris Keenan and Major Derek Thorburns nephew, Ian Maxwell for their contributions to this timeline. Thanks also to Mary Flaws for lending her prized copy of the MOEC Teacher Resource Handbook, by Bryan Dowdle for DoC and the Department of Education published 1988.


Military Sites


    • Motutapu played an important role in Auckland's coastal defence system in WWII.
    • In 1936 a gun battery including 3 gun emplacements was built on Motutapu.
    • Searchlights, observation posts, machine gun posts and a network of storage bunkers were added.

Military Installation

  • Barracks, built to accommodate the guns' crews and support staff at Administration Bay, are used today as an outdoor education camp.
  • A conservation plan for the military installations has been developed and adopted by the Trust.
  • As a first step safety fencing and interpretative signs have been erected through sponsorship from the Sky City Trust.


Gun Emplacements

Motutapu WW11 Gun Emplacements 

The battery was built in the late 1930's to protect Auckland from naval attack. the most likely scenario being that a Japanese naval task force would lead an attack on our harbour. We believe it is one of the most significant and fascinating heritage sites in the entire Hauraki Gulf Maritime Park.

In 1942 when New Zealand was under greatest threat of attack from the Japanese, this gun battery would have been our ground zero if Auckland came under attack. At that time, over the entire Hauraki Gulf, this was the only battery capable of holding off a Japanese cruiser. If these guns had been destroyed, an enemy cruiser could have stood offshore and shelled Auckland harbor and city into submission.

But what of the big 9.2 inch guns at Stony Batter on Waiheke and also on the Whangaparoa peninsula? These guns were immensely powerful, the biggest in NZ but the problem was they were not operational until after the war. They were irrelevant in 1942 when the threat of attack was believed imminent. Construction at Stony Batter didn't start until 1943 and the first gun wasn't delivered till later that year. The second was installed in 1948 and number 3 was cancelled. The two guns were not test fired until 1951. The two gun battery at Whangaparoa was not completed until late 1945.

Most people are unaware that this is the only remaining battery of its type in the southern hemisphere. There was a similar battery built at Palmer Head in Wellington but no evidence remains. The Motutapu Gun Emplacements are also rare because of the large area that the battery encompasses and also because of the remarkable collection of military structures that you can still see around the area.

Construction planning got underway in 1933 with actual construction commencing in 1936. The fort was fully operational between 1938 and 1953.

People often ask why planning to build the Battery started way back in 1933. At that time, NZ was coming out of depression, there wasn't much money about, and there was a labour government in office. We also need to think of this time from an international perspective - from a British, American as well as the NZ perspective.

From the early 1930's the Nazi's were growing in power and many believed the war was eventually going to start up again due to the unfinished business of WW1. Japan was the new threat. There was a lot of friction at the time between Japan and the US and the relationship with Britain was also very strained. Britain was also tending to side with the US more often due to their assistance in WWI.

There were no long distance gun batteries in the Auckland area so it was agreed NZ needed to build a battery. The NZ Government wanted to set the guns up at Milford but the British insisted they be placed on Rangitoto. As Rangitoto was already a reserve, Motutapu was the compromise. The New Zealand government wanted 9.2 inch guns but could only afford six inch guns at the time.

The guns delievered to Motutapu were 6 inch MK21's. There were only 13 of these guns ever built in the world. They were operated mostly by muscle and took 12 men to work each gun. A total of around 75 men worked shifts to operate the guns. They were made in Britain intended for installationon Chilean battleships but the Chileans never fronted with the money. Five of the 13 guns were shipped to New Zealand, 2 went to Palmer Head in Wellington and three here to Motutapu.

The Technical stuff

All the other guns around Auckland in 1942 were short range six inch guns that fired at an angle of up to 20 degrees.   They were simple point and shoot guns.  But Motutapu was unique; they were special Counter Bombardment Guns. Counter bombardment was a technology originally pioneered by the Germans during WW1. They could fire at an angle of up to 45 degrees.  With a range of almost 27km the shells fired over 9000 metres up into the air and fell well beyond the visible horizon (beyond Tiri and Whangaparoa).

Technology known as a fortress system was used to target ships.   It required a very complex system of observation posts (Motutapu/ Matiatia/ Rangitoto summit) with depression range finders to ascertain the range of ships.  This information was communicated to an underground plotting room that processed the data.  It required a new level of sophisticated tactics, communications and calculations.  The result was a very, very accurate gun battery.  Target areas were extensively surveyed and with every firing of the gun, tide, weather and type of shell was entered into the calculations to predict the guns range, bearing and firing time.

This fortress system could accurately coordinate a massive firepower of up to 18 shells per minute. A shell could take one minute to get to the target which meant that 18 shells could be fired before the first one even hit the ground. So each gun could fire up to 6 shells per minute. By comparison, the big 9.2inch guns at Stony Batter and Whangaparoa, when they were finally commissioned, could fire a shell 32km but they could only fire one round per minute.

Early 1942 - period of greatest threat of attack:

In 1942, most of the New Zealand Army were in the Middle East. With few soldiers left there was a desperate effort to improve the defense of the country. The hundreds of men and women who were stationed here definitely expected an attack.

By 1942, there was an immense defensive system being built in the Hauraki Gulf. Motutapu had both advanced ships radar and aircraft radar which was state of the art at the time. Experimental facilities were set up and managed by Ernest Marsden (later Sir Ernest) who had earlier helped another Ernest, Lord Rutherford, to split the atom. The approaches to Auckland were mined all the way from Tiri Island to Motutapu. All shipping was prohibited except through a single channel between Tiri and whangaporaoa. It was a very impressive system poised for action.

The island became an armed camp with up to 800 men and women at different camps across Motutapu. The soldiers had wooden barracks (now the Motutapu Outdoor Education Camp) at Administration Bay with water, electricity, mess halls, a hospital and even entertainment centers. It was a very impressive set up but with most of the New Zealand Army overseas, it was also a very tense time for all concerned. They fully expected to have to defend against invaders arriving by sea or air.

Finally in 1943, there was some welcome news.

The Americans decided that Auckland Harbor would become a US Southern Pacific fleet operating base. This resulted in a massive military build up of troops, ships and aircraft. A huge base was to be built at Yankee wharf on Rangitoto and Motutapu was to become the main storage location for ammunition. The entire area's defence structure was planned to be upgraded to protect the proposed fleet anchorage between Tiri Tiri Matangi and Rangitito.

With tens of thousands of Americans arriving, New Zealand began to relax. Dramatic success in the battle of the Coral Sea had stopped the momentum of the Japanese and the by the end of 1942 the threat to Auckland was greatly diminished. Meanwhile the defenses of Motutapu continued to be improved by adding searchlights (at Billy Goat Point, the northern most point of the island), sonar and moving the command center well underground.

The Guns continued to be practise fired and Motutapu continued to be manned on and off following cessation of hostilities.  The last test firings took place in 1958. The end came in 1962 when the guns were removed and cut up and sold as scrap.

At the Motutapu Trust we believe our Gun Emplacements are an important bit of National history as well as being the critical component in the Auckland WW11 Coastal defence network. We plan to protect, partially restore and interpret this cultural landscape, part of the rich heritage of Motutapu. 

The Gun Emplacements today