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The Royal New Zealand Navy

CHAPTER 15 — Anti-Invasion Mine Defences

page 223

Anti-Invasion Mine Defences

A START had barely been made with the anti-submarine fixed defences before they more or less merged into a far more extensive and expensive programme of anti-invasion measures. During the early part of 1941 growing uneasiness over Japan's aggressive intentions in the Pacific led the New Zealand Government to call in a military adviser to make an estimate of the country's requirements to meet a possible invasion. He was General Sir Guy Williams, KCB, CMG, DSO, who as a former area commander in England had considerable experience in devising anti-invasion plans. His appreciation, which was printed on 1 October 1941, dealt not only with the defences of New Zealand but also with those of Fiji and Tonga for which the New Zealand Government assumed responsibility in November.

On the naval side, he pointed out that fixed defences at defended ports consisted of minefields, indicator loops, and anti-torpedo motorboat booms. These were particularly needed at Auckland with its more numerous approaches and on account of its importance as a base, not only for the New Zealand Navy but also for ships of associated powers which might need its dockyard facilities. When the requirements of Auckland had been met, similar fixed defences should be provided as necessary for the defended ports of Wellington, Lyttelton, and Dunedin in that order of priority.

After that, consideration should be given to the laying of mines in harbours of first-class military importance as a measure of defence additional to shore batteries. Such minefields need not be laid until after the outbreak of war, but the necessary number of mines should be available in the country. These harbours were Bay of Islands, Whangaroa, Queen Charlotte Sound, Tory Channel, Pelorus Sound, and Akaroa. When the minefields had been laid, these harbours, with the possible exception of Tory Channel, should be closed to shipping. Two other harbours of major military importance, namely Port Fitzroy (Great Barrier Island) and Port Underwood, might also be defensively mined.

At the behest of War Cabinet, the Chief of Naval Staff prepared a paper on the measures necessary to implement the Williams proposals. Broadly speaking, the recommendations regarding minefields page 224 were concurred in, subject to certain technical and operational limitations in respect of each field. It was clear, however, that the military adviser's recommendations called for a comprehensive mining organisation.

The only facilities in New Zealand were those being prepared for independent mining at Auckland. This scheme could be expanded, but it was designed for independent mines only. They had been decided upon because they were manufactured in Australia and were readily available, and because the minelayer Bungaree had been promised to lay the field when required.

But if General Williams' requirements were to be met, a controlled mining organisation would have to be set up. This involved the provision of suitable minelaying vessels, a mine depot, a controlled mine base to assemble the mines and their associated gear, advance bases for prepared material in the vicinity of the minefield, adequate mining material and properly trained personnel.

Apart from the depot at Kauri Point, it would be necessary to construct a controlled mine base in a central area and three advance bases at the Bay of Islands, Wellington, and Lyttelton. A plan was being worked out with the assistance of the Public Works Department, initial specifications had been prepared and sites inspected. A preliminary investigation had indicated that owing to technical limitations it would not be worth while to lay minefields in Tory Channel and Pelorus Sound, but all the other specified areas were suitable. Initial requirements, plus a small margin for maintenance, were 11 fields, 11 guard loops, 42 loops, 750 controlled mines, and 600 independent mines.

The estimated cost of the scheme for ships, buildings, and other material was as follows:

Auckland, including two loop minelayers 244,000
Whangaparaoa and Great Barrier Island 64,250
Bay of Islands and Whangaroa 67,500
Lyttelton, Akaroa, and Dunedin 69,000
Wellington, Queen Charlotte Sound, and Port Underwood 110,000
Independent mining items, including coastal minelayer (£230,000) 410,000

An allowance for replacement of mines and equipment brought the total in round figures to £1,000,000. In addition, the annual wages bill was estimated at £111,650.

Forwarding this paper to the Minister of Defence on 27 November 1941, the Naval Secretary said the programme was necessarily a long-range one. It would take about three years to complete, but if page 225 given first priority enough progress might be made to enable initial minelaying operations to be started within eighteen months. The minelaying vessels could be built in New Zealand with imported materials at the expense of the projected programme for building steel minesweepers, but this was not advisable.

The Naval Secretary went on to say that the Chief of Naval Staff was extremely doubtful whether these mining proposals were necessary. The decision must depend upon the importance attached by the Government to precautions against invasion. As had been pointed out in the Williams report, ‘invasion will not be feasible until a series of major disasters to the cause of the British and Associated Powers has taken place.’

However, the Government had approved in principle certain other anti-invasion measures recommended by General Williams, including the mounting of guns in the approaches to harbours other than defended ports. Even if the necessary guns were made available they would not necessarily prevent the entrance of ships. A mining organisation as proposed would be a more effective deterrent, particularly as all the minefields would be covered by guns and so could not be swept.

Nevertheless, in the opinion of the Chief of Naval Staff (Commodore Parry) ‘the maintenance of additional mobile forces (e.g., another cruiser, if the United Kingdom Government could make one available in the Pacific) would be a more effective contribution to the general naval situation than the provision of these static defences which probably will never be required.’

Pearl Harbour and the simultaneous invasion of Malaya decided the matter. The defensive mining proposals outlined by the Chief of Naval Staff were approved in War Cabinet on 15 December 1941. Cabinet said the difficulties of obtaining supplies were well understood, but the Navy was asked to do everything possible to expedite delivery.

The continuous series of ‘major disasters to the cause of the British and Associated Powers’ during the next four months made it appear that the invasion envisaged by General Williams might, before long, be ‘feasible’. The Japanese had exploited their command of the sea (and the air) in the Western Pacific by their masterly use of sea, air, and land forces in a succession of successful invasions. By the end of March 1942 it seemed likely that they would strike westward towards India and southward towards Australia and New Zealand.

As Commodore Parry pointed out in an appreciation of the situation at that time, the latter move would be to deny the Australian and New Zealand bases to the Allied cause. The power to build page 226 up the necessary forces both for present defence and for ultimate operations against Japan depended entirely upon keeping open the sea communications across the Pacific. It was therefore of the utmost importance to hold the islands on the reinforcing route, particularly New Caledonia and Fiji.

What Japan had won by her command of the sea must ultimately be wrested from her by the same means. The defence of New Zealand, Fiji, and New Caledonia depended primarily and mainly upon sea power. If the Allied navies could defeat the Japanese at sea, the latter's invading forces could not survive for long. Even if they attained their objectives, they would be cut off. Unhappily, at that time we could not count on a naval victory. It was therefore essential that the defences of New Zealand, Fiji, and New Caledonia must be made as strong as possible, not only to meet the Japanese threat but to provide adequately defended bases for the use of the United States Pacific Fleet.

But in the early months of the Pacific war the anti-invasion measures in New Zealand were little more than plans on paper. Had the Japanese then been able in the tide of their affairs to take it at the flood in the South Pacific, they would have found no adequate organised defences in being. At that time it seemed that nothing could stem the swift tide of their advance. But, before they could attempt an attack on even Fiji or New Caledonia, let alone New Zealand, the Japanese had sustained their first check in the Coral Sea action. This was followed two months later by the disastrous Battle of Midway. In these two actions, in which the issue was decided by naval aircraft alone, the long arm of sea power had decided the problem of the defence of the South Pacific. Nevertheless, the plans for the defence of New Zealand, with certain modifications, were pushed on to completion at great cost in men, money, and material.

On 21 December 1941 the New Zealand Naval Board informed the Australian Commonwealth Naval Board that it was intended to lay the Auckland minefield as soon as possible, and asked when HMAS Bungaree and the mines would be available. The Australian reply was delayed and, in the meantime, the New Zealand Naval Board put in an order for 600 mines in addition to the 300 already on order. By the time Australia was able to send them the Kauri Point depot ‘would be ready to receive them.’ Replying to both messages on 9 January 1942, the Australian Naval Board said unforeseen demands from the Netherlands East Indies had affected supplies, but the Bungaree was expected to sail for Auckland with a full load of mines on 9 March.

A hastening message from New Zealand on 21 January brought a reproachful reply from the Chief of the Naval Staff, Australia, to page 227 the Chief of Naval Staff, New Zealand. ‘I feel sure you will realise,’ he said, ‘that the limited production of mines in Australia makes a careful review of priority necessary. In view of our agreed policy concerning New Caledonia, I suggest that the mining of Noumea is of the utmost importance.’

The Bungaree sailed from Geelong on 6 March 1942 with a full load of 422 mines and, due to some misunderstanding, headed for Wellington instead of Auckland. In the morning of the 13th she was ordered to proceed direct to Auckland and she passed through Cook Strait a few hours later. She arrived at Auckland on 16 March and began Operation ned next day.

A zigzag line of 200 mines, spaced at 35 to the mile, was first laid across the main channel between Tiri Tiri Matangi Island and Motuhurakai Island. This was supplemented two days later by a line of 200 mines between Tiri Tiri and The Noises rocks off Motuhurakai. Six mines were laid in the Rakino Channel, between the island of that name and Motutapu Island, and a line of sixteen mines was run across the channel on the north side of Rakino. Out of 422 mines laid there was only one failure. The Bungaree left Auckland for Sydney on 20 March.

The controlled mining scheme presented much greater difficulties and was the subject of considerable discussion with the Admiralty, which provided most of the material and the minelaying vessels. On 13 January 1942 the High Commissioner for New Zealand informed Navy Office that the Admiralty had stated the need to convert a suitable vessel for laying and maintaining controlled minefields ‘should they become necessary.’ The drawings and specifications of a typical conversion were not ‘forwarded herewith’ as stated, and as late as April the Naval Board was complaining that they had not arrived.1

Replying to an Admiralty query about the possibility of training officers and ratings to man controlled mining stations, the Naval Board said the Government had authorised the immediate establishment of a controlled mining service. The instruction of personnel could be undertaken if a loop minelayer and an attack teacher could be supplied.

On 21 February the Admiralty reported that 100 observation mines complete with underwater fittings, control equipment for three observation stations, and 60,000 yards of armoured cable were about to be shipped from the United Kingdom. No controlled minelayer could be sent but drawings for a typical conversion job had been forwarded through the High Commissioner. However, it was hoped

1 The drawings and specifications were lost when the ship carrying the mail was sunk by enemy action.

page 228 that the base ship Atreus and the minelaying trawler Alsey which were going out to Australia would be able to assist in New Zealand later.1 Four control stations, two guard loops, and eight mine loops would be sent to New Zealand in time for the arrival of the two ships. More material would be sent at the rate of about one complete station a month, provided it was available and a layer could be converted in New Zealand. A week later the Admiralty said a shipment of 520 mines and sinkers was being arranged.

Revised estimates totalling £674,000 for the controlled mining scheme and 600 independent mines, and an annual wages bill of £90,900 for 45 officers and 250 ratings, were approved in War Cabinet on 6 March 1942. Two days later a site for the controlled mine base at Auckland was selected at Islington Bay, between Rangitoto and Motutapu Islands. Together with the Kauri Point mine depot, the base was given priority among the numerous defence construction commitments of the Public Works Department. But the Islington Bay base was not actually commissioned until 5 January 1943, by which time most of the controlled minefields had been laid. Work at Kauri Point was also very slow, but by July 1942 a large number of mines was stored there. The depot was barely completed at the end of February 1943.

The proposed advanced base at Opua, in the Bay of Islands, was not built. That at Wellington was constructed at Mahanga Bay on the western shore of the outer harbour, there being insufficient space for it at Shelly Bay. It was one of the costly ‘white elephants’ of the controlled mining scheme. The minefield it was planned to serve was laid in November 1942, a fortnight after the Naval Secretary had complained that the base had barely been started! In September 1943 it was put to use to relieve congestion in the transit store at Auckland.

After several sites in Lyttelton harbour had been rejected, Tikao Bay in Akaroa harbour was selected for the advanced base for the Lyttelton area. The Naval Board then decided upon a fully equipped base similar to that at Islington Bay and, a month later, in accordance with a policy of wide dispersion of ammunition reserves, to build eleven magazines at Tikao Bay. The estimated cost of these proposals was £97,440, as against £25,000 for the original base scheme. Authority for the additional expenditure was given by War Cabinet at the end of June 1942. But, following a visit to Tikao Bay in September 1942, the Superintending Armament Supply Officer informed the Naval Secretary that the magazine site was too far by road or sea from Lyttelton, the port to be served. Moreover,

1 The Atreus was a converted merchant steamer of 6546 tons gross register, built in 1911 for the China Mutual Steam Navigation Co. (Alfred Holt & Co.) of Liverpool. The Alsey was a converted trawler of 416 tons, built in 1932.

page 229 the magazines as planned would be only 200 or 300 yards away from the mining depot, with no natural feature to protect the one in the event of an explosion in the other. It was eventually decided to build the magazines at Cass Bay, about two and a half miles from Lyttelton.

The Tikao Bay mining base was not completed till March 1943. It was then manned by an officer and fourteen ratings, all specialists on loan from the Royal Navy. Since a big reduction in the controlled mining organisation was made shortly afterwards, Tikao Bay proved to be a white elephant of even greater proportions than the Mahanga Bay depot at Wellington.

On 10 March 1942 the Admiralty requested the Commander-in-Chief East Indies to sail the controlled mine base ship Manchester City1 and the minelayer Jay to New Zealand as soon as their work at Grand Port, Mauritius, was completed. The Admiralty informed the New Zealand Naval Board that the ships were expected to arrive about the end of April with stores for two minefields. Material for eight more would be shipped shortly. In the meantime the Naval Board should do its utmost to convert a local vessel for minelaying because the Manchester City and Jay would not be able to stay long enough to complete the laying programmes. Suitable officers and ratings should be selected for instruction in controlled minelaying and maintenance on board those ships.

At the beginning of May 1942, however, the Admiralty signalled that owing to the changed situation in the Indian Ocean it would not be possible to spare the Manchester City and Jay, and the Australian Naval Board had been requested to sail the Atreus and Alsey to New Zealand after controlled minefields at Hobart and Sydney had been laid. At that time the latter ships were working in the approaches to Moreton Bay and Brisbane. The Australian authorities on 5 May decided to postpone the laying of fields at Hobart and Sydney, and on learning this the Admiralty asked that the Atreus and Alsey be sent to Auckland as soon as the Moreton Bay fields had been completed. They did not arrive until the end of August, by which time most of the material from England was in hand.

When the Admiralty urged the conversion of a merchant vessel for laying and maintaining controlled mines, the Naval Board was hard put to it to find a suitable ship. Its first choice was the Titoki, a twin-screw steamer of 625 tons gross register, owned by the Anchor Shipping and Foundry Company Limited of Nelson. But when negotiations for requisitioning her were opened, the Shipping Con-

1 Manchester City, converted merchant steamer of 5600 tons gross register; built in 1925 for Manchester Liners, Ltd.

page 230 troller
objected on the ground that she was indispensable to the already depleted coastal coal trade.

After the ship had been successfully tested for stability, with the reluctant consent of War Cabinet, the Naval Secretary stressed the need of haste in converting the Titoki, which, he insisted, was the only vessel available that met all the exacting requirements. The Shipping Controller and the Mining Controller were equally insistent that the ship must be retained in the coal trade. In a letter to the Minister of Mines the latter recalled the difficulties created by the requisitioning of the Anchor Company's Rata and Puriri for use as minesweepers. Of 77,000-odd tons of coal shipped from the West Coast by the Anchor Company in 1941, about 30,000 tons had been carried by the Titoki. The Minister of Mines agreed that ‘a strong protest must be made against this ship being taken from the coal trade.’

In face of this opposition, the Naval Board sought the assistance of Vice-Admiral R. L. Ghormley, USN, Commander of the South Pacific Area. His request of 30 July 1942 to Washington for a suitable vessel brought an offer of the Pine Ridge, a steam collier of 720 tons. The Naval Board cabled assent, and on 30 September 1942 the New Zealand Naval Attaché in Washington reported that he was about to requisition the vessel on lease-lend terms. A month later, however, an officer of the British Ministry of War Transport in Washington, who had had twenty years' experience in the New Zealand trade, declared after inspecting the Pine Ridge that she was quite unsuitable for conversion.

When the New Zealand Joint Staff Mission in Washington reported that further investigation was being made, the Naval Board urged speed because the Atreus and Alsey, which had arrived in August, would have to be released as soon as their work in New Zealand was completed. Thereafter, a vessel would be needed not only for maintenance of the mine loops, but also for the laying and maintenance of harbour defence asdics and indicator loops which could not be worked by the Vesper, a small wooden scow which had been commissioned for cable work on 18 July 1942.

Further efforts to get a suitable vessel from the United States for conversion into a loop minelayer or to replace the Titoki if she were taken were unavailing. In December 1942 the Naval Secretary informed the Minister of Defence that it was proposed to convert HMNZS Muritai. She was by no means ideal and the loss of an anti-submarine vessel must be regarded with some misgiving; but the need of a loop minelayer was ‘extremely urgent’. This hardly tallied with the further statement that strengthening and conversion work on the Muritai would take about six months.

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War Cabinet approval was given on 30 January 1943. A few days earlier the New Zealand Joint Staff Mission reported from Washington that the United States Navy Department had been induced to offer the Wanks, a steamer of 642 tons. The Naval Board received this offer with some coolness and turned it down on the ground that it was too late. But the decision to convert the Muritai was also too late. In June 1943 the overworked Devonport dockyard reported that nothing had been done to the vessel, which could be taken in hand only if urgent repairs to United States ships were refused. The Muritai, which had then been idle for months, was recommissioned as a port M/S A/S vessel on 23 August 1943.

In many parts of the country where naval installations and defences were established, areas of land and sea were prohibited to all and sundry, except, in certain cases, by special permit. For the most part it was merely a matter of gazetting a Notice to Mariners, but where the use of certain channels, harbours, etc., which it was proposed to mine, was virtually essential to the economic life of the community, as in the Marlborough Sounds, serious difficulties arose.

At a conference on 29 April 1942 to discuss the proposed restrictions in the Sounds, it was represented to the naval officers present that they would virtually close down the fishing industry and the Tory Channel whaling station. The movements of coastal shipping would also be disorganised. The declaration of prohibited areas in Pelorus Sound and Port Underwood would also isolate a number of farms. The recommendations of the Senior Naval Officer included drastic restriction, in some cases total prohibition, of the movement of ships and small craft in the various areas. Farmers and their families in Port Underwood and Pelorus Sound to whom access by sea would be denied were to be evacuated. These proposals were approved by War Cabinet on 6 June 1942, with the proviso that a further report be made on the need for removing the farmers.

When the naval authorities reaffirmed the recommendation, War Cabinet ordered an examination of the possibility of providing road access to the farms. The Public Works Department reported on 22 August that the existing tracks to the four farms concerned in Pelorus Sound and six at Port Underwood could be reconditioned at a cost of £4100. The Naval Secretary forwarded this information to the Minister of Defence with a reminder that the Bungaree was to lay the independent minefields in those areas at the end of September. On 25 September 1942 he submitted a draft of The Shipping Safety (Marlborough Sounds) Order 1942.

This order was not promulgated, however, for on 3 October War Cabinet decided that no further action should be taken with reference page 232 to the anti-invasion mines in Port Underwood and Pelorus Sound or the provision of track access to farms in those areas. The Naval Board was directed to investigate the possibility of using the mines at Doubtless Bay, North Auckland, and, in the event of that area being found unsuitable, to consider retaining the mines as a reserve. Restrictions on vessels in Queen Charlotte Sound and Tory Channel were later relaxed to allow fishing and whaling to be carried on.

The Naval Board informed the Minister of Defence on 10 October 1942 that the most effective scheme for Doubtless Bay would be a contact minefield completely cutting off access to the area. In that case the port of Mangonui would be closed to shipping, thus placing an additional burden on road transport. Alternatively, the entire coastline of the North Auckland peninsula could be declared dangerous because of mines, in which case trading vessels would be licensed to enter the area at various ports. Failing approval of such comprehensive restrictions, which would undoubtedly upset the fishing industry, a smaller area outside Doubtless Bay could be declared dangerous. War Cabinet decided that nothing should be done in the matter.

In the meantime the Bungaree had left Geelong with a load of 465 mines for New Zealand. On 21 October 1942 she arrived at the Bay of Islands, where she joined the Atreus and Alsey laying controlled minefields. Next day the Bungaree laid 258 contact mines in two main lines and one short line across the main entrance. She returned to Auckland on 25 October and, after landing the remaining 207 mines for storage at Kauri Point, sailed for Melbourne.

The controlled minelayer Alsey had arrived at Auckland from Australia on 25 August 1942 and the base ship Atreus (Captain J. D. Campbell, RN) six days later. By that time the Japanese were far too deeply involved in the Solomon Islands, where the long struggle on Guadalcanal had begun, to give any thought to New Zealand, where elaborate anti-invasion preparations were still going on.

During the next six months the Atreus and Alsey were to lay eight minefields from Whangaroa in the north to Akaroa in the south. They also trained as many New Zealand officers and ratings as possible so that the efficient operation and maintenance of the controlled minefields would be assured after their departure. Yet, even before the ships had left New Zealand, the first moves were being made in a reduction programme that was to lead to the closing down of the first minefields only eleven months after they had been laid.

The first controlled minefield was laid in Whangaparaoa Passage between the peninsula of that name and Tiri Tiri Matangi Island page 233 in Hauraki Gulf. Much preparatory work had been done at Auckland by a party of three officers and twenty-five ratings of the Royal Navy who had arrived from England in July 1942. The operation began on 4 September and was completed in a fortnight, seven loops of sixteen mines and two guard loops being laid.

The Bay of Islands field was laid during October. It consisted of thirteen loops, each of sixteen mines, across the main channel between Moturoa and Moturua Islands, and three others in the lesser passages. Six guard loops were also put down. This was one of the largest controlled minefields laid by the Royal Navy up to that time.

An observation minefield at Whangaroa was next on the priority list, but as the shore control tower and power-house had hardly been started, the Atreus and Alsey went on to Wellington. By this time it had been decided not to lay minefields in Queen Charlotte Sound and Tory Channel, because comsopac no longer intended to use the sound as a fleet anchorage. A field of eight loops of sixteen mines and two guard loops was laid in Wellington harbour between Gordon Point and the south end of Ward Island. This work was completed on 1 December 1942.

The ships then returned to Whangaroa where, though the control buildings were still uncompleted, an observation field of ten groups totalling thirty mines was laid across the narrow entrance of the harbour. After remedying defects in the Bay of Islands field, the Atreus and Alsey left Auckland for the South Island on 5 January 1943.

When they arrived at Akaroa it was found that little progress had been made with the shore buildings. Temporary huts were set up and the laying of a field of sixteen mine loops and two guard loops was completed by 15 January. A fews days earlier, Captain Campbell of the Atreus was informed by the Naval Board that, because of the ‘change in the strategical situation’, the Lyttelton minefield was not to be laid.

The Great Barrier fields might well have been cancelled for the same reason, but in accordance with orders the ships called at Wellington to remedy defects in that field and then proceeded to the island. There again they found the shore buildings in an embryonic state, compelling the use of portable huts. Five mine loops and two guard loops were laid across the entrance to Port Abercrombie and an observation field of forty-three mines in Governor Pass, the narrow southern entrance to Port Fitzroy.

The Atreus and Alsey returned to Auckland on 18 February for overdue docking and repairs. After that they were detained in New Zealand waters for some weeks longer remedying defects in page 234 the minefields in Whangaparaoa Passage and at Wellington, no New Zealand vessel having been converted for this purpose. The Atreus left Wellington for Melbourne on 4 April 1943 and the Alsey sailed five days later.

An offer by Australia on 12 December 1942 to make the Bungaree available for operations in New Zealand after March 1943 led to a survey of mining policy. The Staff Officer (Torpedo and Mining) contended that the changed strategical situation in the Pacific had relegated Auckland to a rear base status and that anti-invasion minefields were a waste of money and material. He advised against reinforcement of the Auckland independent minefield, but in case the Naval Board decided to do so, he submitted alternative schemes. One was to reinforce the existing field with a similar field and the other to support it with an anti-submarine field, since submarine attack was about the only possibility to guard against. If it was decided not to use the 800 available mines in that way, they should be offered to the United States naval authorities.

The position was explained to comsopac, who replied on 25 January 1943 that he did not need the mines and agreed that they should be used to reinforce local fields. The Bungaree was engaged in mining operations on the Great Barrier Reef at that time, but the Australian Naval Board agreed to send her to New Zealand about the end of June.

No sooner had this been settled than comsopac asked for the Bungaree to reinforce the minefields at Noumea, New Caledonia, using the mines stored at Auckland. The New Zealand Naval Board thereupon cancelled its plan for reinforcing the minefields at Auckland and the Bay of Islands. The Bungaree arrived at Auckland from Sydney on 12 July 1943, loaded 446 mines, and sailed five days later for Noumea, escorted by HMNZS Tui. She returned to Auckland on 4 August for the remaining 349 mines, which were duly laid. This was a useful disposition of approximately 800 mines which, for no apparently good reason, the Naval Board had planned to sow in the Auckland area after a previous decision not to lay any more minefields.

A series of vigorous minutes by the Staff Officer (Torpedo and Mining) in January and February 1943 had expressed the uneasiness he felt over the ‘extravagant and unnecessary use of valuable war material, manpower and labour’ on the controlled mining programme. He was ‘unable to understand why this colossal expenditure and organisation was ever implemented against the Naval Board's strong recommendation to the contrary….’ The time had arrived when ‘everything should be devoted to the offensive, not to static defence schemes.’

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After a survey of commitments involving large quantities of material and equipment and 44 officers and 245 ratings to man the controlled mining stations, he said that if the full programme was carried out all the equipment received so far would be exhausted. Orders for spares should be cancelled and the Whangaroa, Great Barrier, Lyttelton, and Tikao Bay projects abandoned, thus effecting a saving of about £100,000. The mine depot at Kauri Point should become part of the Armament Depot, which badly needed space for stores and ammunition.

The principle, but not all the details, of SOTM's recommendations was accepted by the Naval Board which, on 25 February 1943, submitted a modified mining policy to the Minister of Defence. It had already instructed the High Commissioner in London to cancel orders in hand for controlled mining equipment. It proposed that no more minefields be laid and that the controlled fields at Auckland and Wellington be maintained by using spare material. The conversion of the Muritai should be gone on with to provide a vessel for this work. These recommendations were approved in War Cabinet on 19 March 1943, by which time the Atreus and Alsey had just completed laying the minefields.

The position was again surveyed in June 1943 by SOTM, who remarked that £1,500,000 had already been spent on ‘this colossal static programme inaugurated by a Government with the jitters, contrary to naval advice.’ After questioning the value of each controlled minefield in turn, he said it was clear that maintenance of all except those at Auckland and Wellington was a waste of manpower and money. Conversion of the Muritai would cost £30,000 and take at least ten months, by which time deterioration of the minefields would entail the lifting and refitting of every mine loop. He proposed that the existing stations be manned as long as they were operative, after which the mines should be lifted or fired. Islington Bay should be paid off as a controlled mining base and used for storage purposes.

But the Naval Board procrastinated by recommending to the Minister of Defence that the situation be further reviewed at the end of the year, when consideration should be given to requesting Australia to make a vessel available to recondition the minefields not later than June 1944. Alternatively, at that time, ‘should the general situation warrant it,’ the Government should consider accepting further deterioration in the efficiency of the minefields and rely solely on anti-submarine vessels and anti-submarine fixed defences for the safety of the ports. No ministerial decision appears to have been received by the Board.

A conference presided over by the Chief of Naval Staff and attended by the other naval members of the Board, naval officers-in- page 236 charge, and staff officers was held on 28 September 1943 to consider ‘reductions in the scale of the naval defences of New Zealand proposed as a result of the improved strategic situation and the necessity for conserving manpower.’

In respect of the minefields, it was agreed that the independent minefields in Hauraki Gulf should remain at present, except those in the channels on either side of Rakino Island, which were to be swept. The controlled minefield in Whangaparaoa Passage was to be reduced to a care and maintenance basis and that at Wellington to remain fully manned, the position in respect of both to be reviewed early in 1944. The independent minefield at the Bay of Islands was to be swept and the controlled fields there and at Whangaroa, Great Barrier, and Akaroa to be fired. All stores were to be transferred to Islington Bay and Tikao Bay base was to be closed down and offered to the Army.

The few mines in the Rakino channels were swept during October 1943 but War Cabinet's approval in regard to the other fields was not given until the end of the year. In January 1944 it was decided to dispose of all the minefields except that at Wellington. The Akaroa controlled field was fired in February and sweeping of the Bay of Islands independent field completed about the same time. Thereafter, firing and sweeping operations continued until July 1944, when they were completed by the destruction of the controlled field at Wellington.

The prophecy of Commodore Parry as Chief of Naval Staff in November 1941 that static mine defences would probably never be required had been completely fulfilled. Doubtless at that time the Government had felt bound to act on the advice of their military adviser, General Williams, regarding the defence of New Zealand against a possible Japanese invasion, which to many appeared a near probability in the black months following Pearl Harbour. But, though it could not be known at the time, Japanese sources have since revealed that no attack on New Zealand was ever planned.

In any case, the defensive mining of harbours was a long-term programme. It took months to bring the necessary equipment from overseas and the ships to instal it did not arrive in New Zealand until August 1942. By that time there was a definite improvement in the strategic situation in the Pacific. New Caledonia, Fiji, Samoa, and other island bases on the oceanic lines of communication were well garrisoned and reasonably secure. The decisive actions of the Coral Sea and Midway had been fought and won by the Americans, who were using New Zealand as a southern base for their powerful thrust into the Solomon Islands. But the immensely costly mining programme went ahead for months almost in its entirety, adding to the almost intolerable strain on the country's resources of manpower page 237 and material. While there were huge commitments in respect of the other two services, the Navy was also concerned to get an extensive programme of works completed in its main base at Devonport Dockyard and the subsidiary base at Wellington, as well as to institute its anti-submarine defences, including the building of anti-submarine trawlers and launches.

The moral of all this is that the sure defence of our island country depends first and foremost, like that of the British Empire as a whole, upon the security of our sea communications, and that implies adequate naval strength. It was Japan's command of the sea that gave her initial success in an incredibly short time. It was the immense build-up of American sea power that brought her to ultimate defeat. Another lesson to be learned by New Zealand is that a healthy and vigorous mercantile marine, especially in coastal shipping and fishing vessels, is essential to our security. For it is to the pool of merchant shipping that the Navy must look to furnish the numerous auxiliary vessels needed in time of war. The real British Navy is still all British shipping and all British seamen.