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