The Royal New Zealand Navy
CHAPTER 12 — Minesweeping in New Zealand Waters
Minesweeping in New Zealand Waters
THE experience of the First World War indicated that the most likely danger to shipping in New Zealand waters in the event of another war would be enemy raiders and mines laid by them. In November 1916 the German raider Wolf sailed from Kiel under orders to ‘interfere with shipping in distant waters….’ During a cruise of fifteen months she sank twelve ships and laid eight minefields in the Indian and Pacific Oceans which caused the loss of eight vessels and damage to others. While in New Zealand waters in June 1917 the Wolf laid twenty-five mines off the Three Kings and thirty-five off Farewell Spit. She then crossed the Tasman Sea and laid thirty mines near Gabo Island on the coast of New South Wales. These minefields caused the loss of three steamers, the Cumberland, 9470 tons, off Gabo Island on 6 July 1917, the Port Kembla, 4700 tons, off Farewell Spit on 18 September 1917, and the Wimmera, 3022 tons, off the Three Kings on 26 June 1918.
The fishing trawlers Nora Niven and Simplon were requisitioned by the Government and equipped as minesweepers. They swept seventeen mines off Farewell Spit and eighteen in the Three Kings area. Others had probably sunk or broken adrift. The two little fishing boats of 1918 were the forebears of the Royal New Zealand Navy's numerous minesweepers of the Second World War. The Nora Niven herself survived to take a small part in their activities.
1 The Shipping Sub-Committee consisted of representatives of Navy Office, Marine Department, Defence Department, and Department of Industries and Commerce. The Committee of Imperial Defence (NZ Section) was reconstituted in 1936 as the Organisation for National Security.
The Naval Board in September 1938 decided that, as there obviously were not sufficient suitable vessels available to provide a minesweeping flotilla for each of the main ports, a single flotilla would be formed and ‘operated as a unit in accordance with the demands of the general situation.’ For this purpose six vessels would be requisitioned immediately in an emergency and another three would be added ‘as soon as possible.’ Each vessel would be fitted out for both minesweeping and anti-submarine duties. Performance fell short of this plan in 1939.
In February 1939 it was decided to build three vessels as mine-sweeping, gunnery, and torpedo training ships. Cabinet authority for a total expenditure of £170,000 was given on 2 May 1939. The tender of Henry Robb Ltd., of Leith, Scotland, was accepted on 26 September. The price quoted was £58,000 for each ship, afloat at Leith, subject to any increases in wages and costs of material and exclusive of war risk insurance during construction. The builders' price for each ship subsequently rose to about £80,000. Owing to pressure of Admiralty work in the shipyard, the keels of the ships were not laid until 22 March 1940. Early in April 1940 the Naval Board approved the names of Moa, Kiwi, and Tui for the ships. Many delays occurred in their building and they did not arrive in New Zealand until well on in 1942.
On 2 September 1939 the Shipping Requisitioning Emergency Regulations came into force with the proclamation of an emergency. In the preceding months the naval authorities had inspected and selected fifteen vessels for possible conversion to minesweepers. Of these the Auckland-owned trawlers James Cosgrove, Thomas Currell, and Humphrey were chosen for immediate conversion. They were quickly fitted out, the James Cosgrove being commissioned for service on 10 October 1939 and the others six days later. The James Cosgrove was manned entirely by officers and ratings of the RNR and RNVR, the others by both merchant marine and naval personnel. The masters of the Thomas Currell and Humphrey were given temporary naval rank and retained in command.1
1 The James Cosgrove was commissioned by Lieutenant-Commander H. W. Jones, RNZNR, the Humphrey by Lieutenant A. G. Nilsson, RNZNR, and the Thomas Currell by Lieutenant J. Holt, RNZNR.
The Shipping Requisitioning Emergency Regulations provided for the hire of vessels at rates agreed upon by the Treasury, the Marine Department, and the owners. Where agreement could not be reached, the matter was to be decided by arbitration. This charter system proved very costly and the regulations were amended on 29 November 1939 to enable the Government to acquire vessels by compulsory sale and purchase. The James Cosgrove, Thomas Currell, and Humphrey accordingly were purchased from Sanford Ltd., of Auckland, at a cost of £22,500.
During the early months of the war the Wakakura intensified her training activities, Lieutenant-Commander Holden, RNZNR,1 being appointed to her in November 1939 as officer instructor to the RNZNVR and Senior Officer, New Zealand Minesweeping Flotilla.
In the meantime preparations were made for taking over three additional vessels for minesweeping purposes. The Navy had set its heart on the trawlers South Sea and Futurist, but the Secretary of the Marine Department informed the Naval Secretary that, as three trawlers had already been taken, the withdrawal of another two would seriously dislocate the fishing industry. The matter was referred to the Fisheries Advisory Committee of the Food Supply Control Commission, which reported to the Minister of Supply that the South Sea and Futurist were practically indispensable to the fishing industry, because the former was parent ship of the fishing fleet at the Chatham Islands, whose entire catch was exported to Australia and earned a large fraction of New Zealand's sterling funds, and the Futurist caught 30 per cent of the fish supply for Wellington. It was agreed that the two trawlers should be equipped as minesweepers and then returned to the fishing industry until such time as they might be required for naval service.
1 Captain A. D. Holden, OBE, DSC, RNZNR; born England, 17 Feb 1901; merchant marine officer; chief officer MV Maui Pomare, 1933–39; minesweepers, RNZN, 1939–44, RN 1944–47: Commander, Jun 1940; Captain, Dec 1945.
Commodore Parry said it was his duty to inform the Government that the four minesweepers in commission were ‘totally inadequate to ensure even reasonable security from enemy minelaying activities.’ The first warning of an enemy minefield was ‘likely to be the destruction of one or more ships, except in so far as the present minesweeping flotilla is able to carry out occasional searching sweeps.’ It would be evident to Ministers that four minesweepers could not conduct searching sweeps around the coasts of New Zealand to any but a most limited extent; and in the event of mines actually being discovered, the area which could effectively be swept by four vessels was so small that it would take a considerable time to clear a minefield of any size; in the event of more than one minefield being laid it might be days before the second field could be dealt with. The lack of any danlaying vessels1 would still further delay mine clearance operations.
Commodore Parry urged that approval be given to take over the South Sea and Futurist and maintain them in commission, giving a total of six minesweepers; to equip and commission two suitable vessels for danlaying duties and two wooden vessels as anti-magnetic minesweepers. He further suggested that ‘minesweeping requirements should take precedence over other considerations at this stage of the war. Every possible safeguard would be imposed to reduce the possibility of vessels being found unsuitable after being taken up.’
In less than three weeks his warning was borne out by the event. Shortly before four o'clock in the morning of 19 June the Canadian-Australasian Royal Mail liner Niagara, 13,415 tons, outward-bound from Auckland for Suva on passage to Vancouver, struck a mine six miles east from Maro Tiri Islands (Hen and Chickens) and sank in deep water. Fortunately, there was no loss of life, the passengers numbering 136 and the crew of more than 200 getting away safely in the ship's boats. Included in the Niagara's cargo was a shipment comprising one-half of the New Zealand stock of small-arms ammunition which was being sent to England to assist in making good the shortage existing there after the evacuation of Dunkirk. In the ship's strongroom was stowed nearly eight tons of gold ingots, valued at £2,500,000, from South Africa, which had been shipped for the United States.
1 A danlayer is a small vessel (sometimes a minesweeper) employed in minesweeping operations to lay dan-buoys to mark the limits of the channels swept through a minefield.
Objections from the Government and the fishing industry to the taking over of certain vessels vanished overnight when the news of the loss of the Niagara was received. Cabinet approval was given immediately for the requisitioning of the trawlers South Sea and Futurist for permanent service as minesweepers, the 50-ton wooden vessel Coastguard to serve as a danlayer, the trawler Nora Niven on a temporary basis for sweeping at Wellington pending the arrival of the South Sea from the Chatham Islands, and the harbour passenger vessel Duchess, temporarily in the first instance, as an additional sweeper at Auckland. The last-mentioned vessel was unsuitable for sweeping in any but sheltered waters. These four sweepers and the danlayer were to be manned by naval crews, though members of their existing crews who volunteered to train were to be fitted in if possible.
On the morning of 19 June the Wakakura and Humphrey were undergoing refits in the dockyard, and only the James Cosgrove and Thomas Currell were able to go to sea when the Niagara's distress signals were received. The Senior Officer Minesweepers, Lieutenant-Commander Holden, embarked in the James Cosgrove and the two trawlers sailed from Auckland at 7.20 a.m. Proceeding at full speed, they arrived at 12.50 p.m. close to the position given by the Niagara and began sweeping on a northerly course. At 2.48 p.m. the Thomas Currell reported a mine in her sweep and a minute later the James Cosgrove also swept a mine. Both mines, which were clean and freshly painted, were of the contact type, each with five horns. They were sunk by rifle fire.
Beginning at first light on 20 June, the James Cosgrove and Thomas Currell, on the orders of Commodore Parry, began a searching sweep of Colville Channel, the eastern approach to Hauraki Gulf, which was to be used by shipping while the Maro Tiri minefield was being swept. The course of the sweep was from one mile east of Channel Island light to a position eight miles east of Cuvier Island and on to the 100-fathoms line.
The loss of the Niagara and the discovery of the mines were the first indications of the presence of a German raider in the South Pacific. The main ports were closed to shipping while minesweepers carried out searching sweeps in the approach channels to the harbours. When traffic was resumed, the inter-island passenger steamers made the passage between Wellington and Lyttelton in daylight.
On 21 June Commodore Parry issued a minesweeping programme to deal with the situation as efficiently and rapidly as the meagre page 172 force at his disposal would permit. Briefly, the minesweeping flotilla (Wakakura, James Cosgrove, Thomas Currell, Humphrey, and danlayer Coastguard) was ordered to sweep out of Auckland at 10 a.m. on 22 June and proceed to Wellington, sweeping off East Cape, Portland Island (Mahia Peninsula), and from Cape Palliser inward to Wellington by 25 June. There the Futurist and Nora Niven were to join the flotilla, which would sweep the western approach channel on the 26th, before moving south to sweep the approaches to Lyttelton.
In the meantime searching sweeps off Port Nicholson had begun. The South Sea was at the Chatham Islands and the Futurist and Nora Niven, though not completely fitted out, were pressed into service. The Futurist swept off Wellington for eight hours on 21 June, after which the Nora Niven took over and the former sailed for Lyttelton. From 23 June till 2 July the Futurist searched the approaches to Lyttelton, while the Nora Niven did the same at Wellington.
The flotilla from Auckland was well south of East Cape in the afternoon of 23 June when it was ordered to return immediately. The reason for this sudden change was a signal received by Auckland Radio from the Shaw Savill and Albion motor-vessel Waiotira which reported having sighted a mine, probably cut adrift by her paravane, in a position about nine miles east-south-east from Cuvier Island.
The minesweepers were ordered to search the area and then sweep ahead of a convoy from Channel Island out to the 100-fathoms line. In a rough sea the flotilla began working about seven o'clock on 25 June from a position 12·8 miles east by south from Cuvier light. Two hours later the James Cosgrove swept a mine, which was sunk by rifle fire. Sweeping was stopped for about three hours by unfavourable weather and resumed at midday. No more mines were found and the channel was considered clear for the convoy of seven merchant ships which, preceded by the minesweepers and led by the Remuera, passed through safely next day.
On 28 June the flotilla divided, the James Cosgrove and Thomas Currell remaining in the Auckland area and the Wakakura and Humphrey sailing for Wellington and Lyttelton, off which ports during the next fortnight they carried out searching sweeps which established the immediate safety of the approach channels and the probability that no mines had been laid in those localities. They also made a sweep off Cape Campbell, and from 12 to 15 July searched the vicinity of Cape Farewell, a focal area for shipping bound to or from Australia and the west coast of the South Island in which the raider Wolf had laid mines in June 1917. Meanwhile, the James Cosgrove and Thomas Currell working in Colville Channel had swept and sunk three more mines in the northern approach between page 173 Great Barrier Island and Cuvier Island. A number of merchant vessels was also ‘swept’ in or out through the approach south of Cuvier Island.
In a memorandum to the Minister of Defence, dated 5 July 1940, the Chief of Naval Staff set out his revised policy to meet the position arising out of the discovery of the Hauraki Gulf minefield and the possibility of further minelaying by the enemy. He considered that the minimum minesweeping strength should be a mobile flotilla of at least six sweepers and a pair of sweepers at each of the main ports of Wellington, Auckland, and Lyttelton. Thus the aim was at least twelve sweepers, and two danlayers would also be needed. The scheme which the Government was preparing for building trawlers in New Zealand and purchasing others to be built in Australia was no solution to the urgent problem of providing minesweepers for immediate service and had no bearing on policy for the time being.
The Nora Niven had proved unsuitable for sweeping, owing to lack of power and inadequate crew accommodation, and would be returned to her owners. In her place the Muritai1 was being taken up for permanent service and fitted out at Wellington with winches from the steamer Port Bowen, stranded near Wanganui, which had been acquired by the Government for breaking up. The Duchess was completing fitting out in the dockyard at Devonport and, though possibly too small, would be retained in the meantime as a port sweeper at Auckland. Should the policy of maintaining twelve minesweepers be approved, it would be necessary to select four additional vessels from the Matai, Arahura, Rata, Gale, Breeze, and Rangitoto, named in order of probable suitability.
The organisation and broad operational activities of the minesweepers were laid down by the Naval Board on 18 July as follows:
First Group: Wakakura, Futurist, South Sea, James Cosgrove, Thomas Currell, Humphrey and danlayers.
Auckland – Duchess and one other;
Wellington – Muritai and one other;
Lyttelton – two not yet allocated.
1 Muritai, harbour ferry steamer, 462 tons; built in 1922 for Eastbourne Borough Council; commissioned 25 September 1940.
On 5 August 1940 a message was received by HMS Philomel from an amateur wireless station on Great Mercury Island reporting that Mr D. McKay, skipper of the fishing launch Ahuriri, had found a drifting mine one mile north-west from Richards Rock (two miles north of Red Mercury Island) and towed it into Mercury Island Bay. The Squadron Torpedo Officer, Lieutenant-Commander P. P. M. Green, RN, with a junior officer and three ratings, sailed in the Humphrey for Great Mercury Island, where they found that McKay had stood by the mine all night in his dinghy. He had moored the mine with a boat anchor secured by a line to one of two ringbolts on the side of the mine. He informed Green that he had seen a merchant ship passing close to the spot where he later discovered the mine and, reasoning that other ships would pass that way, he felt it was his duty to do what he did.
The mine was towed inshore and beached in a cove where, at low tide, the work of dismantling it was begun. The mooring wire had been cleanly cut as though by a ship's paravane. When the mechanism plate had been cleared of sand, the switch was found to be at ‘A’ and the mooring spindle ‘in’ – a safety pin was inserted to prevent its coming ‘out’. When the large nut securing the detonator carrier was slackened, there was an alarming rush of air and the party withdrew for two minutes. The mechanism plate had to be unbolted and taken off before the primer could be removed. After the explosive charge had been taken out, the empty mine was refloated and towed to the Humphrey, which took it to the base at Devonport. Before leaving, Lieutenant-Commander Green detonated the mine charge. He praised the good work of McKay, who had served in minesweepers in the First World War and ‘so was fully aware of the risks he was running, without being possessed of the requisite knowledge to safeguard himself.’
The Duchess, port sweeper at Auckland, was ordered to sweep in the Colville Channel on 8 August and, on the following day, to sink a drifting mine reported by the fishing launch Waimana off Charles Cove, near Cape Colville. The mine was found and sunk on 10 August.
1 Mr McCracken was awarded £5. Owing to the special circumstances in his case, Mr McKay was paid £10.
At the beginning of August 1940 the Matai, Puriri, Rata, and Gale were selected for conversion to make up the required complement of twelve minesweepers, and the Kaiwaka was chosen as a danlayer.1 To meet the objection that withdrawal of the Puriri, Rata, and Gale would cause serious difficulties in the coastal cargo trade, the Minister of Marine, at a conference with the shipowners on 23 August, said a group of fast minesweepers to carry out clearing sweeps was urgently needed by the Navy. Some means must be found whereby, with the assistance of the railways and road services, the New Zealand shipping industry ‘could get together, pool its resources, re-organise its system, and arrange that the sea-borne carrying which is essential, shall be carried out by the ships which remain for commercial purposes after the Navy has taken these three ships.’ On the following day the New Zealand Shipowners' Federation reported that the Puriri, Rata, and Gale would be handed over and the necessary arrangements made to carry on the coastal trade without them. The New Zealand Refrigerating Company protested that the Kaiwaka, which had been specially built for lightering meat cargoes at Wanganui, could not be replaced. The loading of overseas vessels in the roadstead of that port had always been a slow business and the withdrawal of the Kaiwaka would make it even slower. In wartime it was vital that the rapid turn-round of ships should be maintained. For that reason, a decision on the taking-over of the Kaiwaka was postponed.
Meanwhile, the minesweeping trawlers in service carried on their searching sweeps at the three main ports of Auckland, Wellington, and Lyttelton. Another mine was swept on 15 August about 11 miles south-east from Cuvier Island. The South Sea was commissioned at Wellington on 12 August and the Futurist on the 31st.
1 Matai, Marine Department lighthouse tender; 1050 tons; built 1930. Puriri, coastal motor-vessel; Anchor Shipping Co. Ltd.; 938 tons; built 1938. Rata, coastal steamer; Anchor Shipping Co. Ltd.; 974 tons; built 1929. Gale, coastal motor-vessel, Canterbury Steam Shipping Co. Ltd.; 622 tons; built 1935. Kaiwaka, motor-powered cargo lighter; NZ Refrigerating Co. Ltd.; 169 tons; built 1937.
On 9 September the trawlers began searching sweeps in the passage through Jellicoe Channel (SCM 11) west of Little Barrier and the Maro Tiri islands, to a point beyond Cape Brett. The Muritai was commissioned as a minesweeper at Wellington on 25 September. A drifting mine was reported on 8 October by the fishing launch Cobra, three miles south-west of Port Tryphena, at the southern end of Great Barrier Island. It was found next morning by the danlayer Coastguard, which took it in tow and moored it about a mile outside the bay. Later in the day it was again taken in tow until the Duchess was met, when she sank it by rifle fire.
A scheme for building minesweeping trawlers in New Zealand to meet the Navy's stated requirements was discussed at a conference on 31 May 1940, attended by representatives of the Navy, the Marine Department, the Fishing Industry Advisory Committee, the railway workshops, and other Government Departments. It was considered feasible to build six ‘Castle’ type trawlers within a year under the direction and supervision of the Marine Department. On 1 June Cabinet approved this proposal and some weeks later authorised the construction of another six trawlers. Actually, nearly two years elapsed before the first of these vessels was completed and commissioned for service.
A start was made on 21 October 1940 by an Auckland firm on the building of the first trawler, which was named Manuka. She was of composite construction, that is, of kauri planking on steel frames. Two similar vessels, named Rimu and Hinau, were laid down at Auckland soon afterwards.2 The engines and boilers for these vessels were supplied from old steamers purchased by the Government from the Northern Steamship Company.
1 When the Niagara was sunk in June 1940 she was carrying in her strongroom about eight tons of gold ingots from South Africa, packed in 295 boxes and valued at approximately £2,500,000, which had been shipped for the United States. The recovery of the greater part of the gold from the lost liner lying at a depth of 438 feet was one of the most remarkable and successful salvage operations of its kind ever undertaken. It was carried out in a minefield whose exact limits were unknown and, despite many difficulties and delays due to mines, stormy weather, and other hazards, was completed in barely twelve months. In the course of the operation the divers made more than 300 descents, three of which reached a depth of 528 feet. The New Zealand Navy can justly claim some share in the ultimate success of the project. Its minesweepers cleared the area of mines and much equipment was supplied and assistance given in other ways, notably in solving difficult problems in the use of explosives in record depths of water.
2 The Manuka was commissioned on 30 March 1942, the Rimu on 15 July 1942, and the Hinau on 23 July 1942.
The Chief of Naval Staff had indicated in his first report of 29 May the possibility that magnetic mines might be laid in New Zealand waters.2 On 7 August Cabinet approval was given for the requisitioning of two small, wooden, coastal cargo vessels, Kapuni and Hawera, whenever the special gear required to fit them out as magnetic minesweepers was received from England. The Kapuni was taken over on 16 January 1941 and the Hawera six months later, but it was a long time before they were fitted out and commissioned.3
As a second danlayer would be indispensable when clearance sweeps of the Hauraki Gulf minefields were started, the Navy pressed for the taking over of the Kaiwaka, to which strong objection had been raised by her owners, the New Zealand Refrigerating Company. At the beginning of August 1940 the Minister of Marine reported to the Prime Minister that the Kaiwaka could be spared for naval service provided that a fairly large proportion of Wanganui refrigerated and other cargo was railed to Wellington for loading into overseas ships. The question of discontinuing the loading of ships in Wanganui roadstead had not been finally settled when, on 7 January 1941, War Cabinet approved the taking over of the Kaiwaka for conversion into a danlayer. She was delivered to the naval authorities on 5 March and commissioned for service on 21 May 1941.
1 The steel minesweepers commissioned were Aroha, Awatere, Hautapu, Maimai, Pahau, Waiho, Waima, and Waipu. They measured about 290 tons gross register, on a length of 125 feet, a breadth of 23 feet, and a depth of about 13 feet.
The fishing launch Tuna had reported sighting a mine off Rangipuke Island in the Firth of Thames on 28 January 1941, and on the following day the military authorities reported that a mine had drifted ashore at Ohakeao Point, on the south-west side of Coromandel harbour. These reports were considered to concern one and the same mine. When a naval party under Lieutenant R. J. Greening, RN, arrived at the harbour, it found that the mine had been secured on the foreshore with fencing wire. It was close to a house on the Coromandel–Thames road. It was rendered safe by removing the primer and the explosive charge, which was destroyed. A reward of £5 was paid to the master of the Tuna and letters of commendation were sent to four local residents who helped the naval party to dispose of the mine.
The Wellington-based minesweepers bore the responsibility for searching sweeps off Cape Farewell. No mines were laid there during the Second World War, but the possibility was too strong to be ignored. A channel was swept from a position 10 miles north of Farewell Spit lighthouse and then 10 miles west, and this was widened to two miles by the James Cosgrove in March 1941. The South Sea swept the channel from a position eight miles north of Farewell Spit light about the end of March while the James Cosgrove was sweeping SCM 12 into Wellington.
The Hauraki Gulf minefields by that time had been in existence about nine months – long enough for corrosion and the action of the sea to have done their work on insecure and faulty moorings. Drifting mines were reported from widely separated positions during March 1941. On the 20th the Thomas Currell, port sweeper at Auckland, sighted and destroyed a mine about four and a half miles north by east from Flat Rock, off Kawau Island, that is, well inside Hauraki Gulf. Three days later the motor-ship Maui Pomare reported passing a drifting mine in a position about 120 miles to the northward of East Cape; yet another was sighted on 24 March about 24 miles north-east of Mayor Island in the Bay of Plenty. As a result of these reports the Naval Board broadcast a signal to all British merchant ships in the area of the New Zealand Station warning them that drifting mines might be met between East Cape and the approaches to Auckland as far out as 200 miles off the coast. All vessels were warned to keep a sharp lookout for mines when rounding East Cape.
The Matai and the Gale were commissioned as fast minesweepers at the beginning of April 1941, the former on the 1st and the latter page 179 two days later. During the month sweeps were made in the Cradock Channel (between Great Barrier and Little Barrier) in the course of which a mine was swept in a position about 10 miles south-east from Moko Hinau light. The Puriri was commissioned on 19 April and the Rata on 14 May 1941. The Duchess, which had proved to be unsuitable for minesweeping and was badly in need of a refit, was laid up at Auckland.1
On 13 May the naval launch Rawea (Sub-Lieutenant Bruton, RNZNR)2 was stopped by the fishing launch Pearline, which reported having fouled a mine when hauling her net. She had marked the position with a flag buoy about nine miles north-east by north from Bream Head. The Rawea found the buoy about eight and a half miles north-east by east from that point. Bruton and a volunteer rating hauled in thirty feet of the Pearline's line before the mine came into view about six feet under water, and in that position it was secured to the buoy. The Gale and Puriri, which were under orders to sweep the Jellicoe Channel, received a signal from Auckland to get into touch with the Rawea and assist in destroying the mine. The senior officer in the Gale learned from the Rawea that the mine had been buoyed and that the buoy had not shifted all day. As it was nearly dark, he decided to leave the sweeping of the mine till next day and, after fixing the position of the buoy, rejoined the Puriri in Urquhart Bay. He instructed the Puriri to leave at daybreak for a position off Bream Head and sweep to the northward of that point.
At daybreak the Gale left the anchorage and proceeded in a rough sea and poor visibility toward the approximate position of the mine. Her commanding officer noticed that the Puriri was following but did not give her any specific orders. When she failed to sight the buoy the Gale steered two miles to the northward and then turned to the southward, followed by the Puriri right astern. Again the buoy could not be found and the Gale turned to starboard in a circular movement. She had completed about a quarter of the circle when she found by bearings of Maro Tiri that she was in the exact position of the night before.
The foregoing narrative was compiled from the minutes of evidence taken by a naval board of inquiry which found, inter alia, that the Puriri was lost by striking a mine previously reported and for which she was searching in company with the Gale. Blame was attributable to the senior officer of the searching ships ‘in that he did fail to carry out an organised search and to take proper charge of HMS Puriri.’
Thus, before the sweeping of the Hauraki Gulf minefields had begun, one of the five fast minesweepers allocated for the task had been lost. The Anchor Shipping and Foundry Company, Ltd., of Nelson, owners of the Puriri, were granted compensation in accordance with the terms of the charter party, amounting to £65,003 8s. 6d. The Navy searched the shipping lists to find a replacement for the Puriri and decided that the motor-vessel Breeze, a sister ship to the Gale, was the most suitable ship. Her owners, the Canterbury Steam Shipping Company Ltd., protested that the requisitioning of the Breeze would ruin their trade which had been built up over thirty years. They had willingly surrendered one-third of their total tonnage and were strongly opposed to any further loss ‘until all other coastal shipping companies have made an equal contribution.’ War Cabinet considered the removal of the Breeze from trade should be avoided if possible, but finally consented to her being requisitioned. She was handed over to the Navy in March 1942, but was not commissioned for service until 24 October 1942, five weeks after the sweeping of the Hauraki Gulf minefields had been completed.
New Zealand naval local defence policy during the first eighteen months of the war had been concerned mainly with the most urgent requirement, the selection and fitting out of suitable vessels for minesweeping. The Admiralty had recommended that all vessels selected for the dual purpose of minesweeping and anti-submarine operations should be suitable for asdic installation. Now that asdic equipment had been obtained and suitable vessels for carrying and operating it were in commission, the Naval Board decided to equip them as opportunity offered. By 15 August work on the Muritai was completed and her asdic tested and found satisfactory in all respects.
In the meantime the 25th Minesweeping Flotilla, less the Muritai, had sailed from Auckland on 3 July, but bad weather forced it to shelter in Urquhart Bay for three days, after which sweeping was resumed outside Maro Tiri light. Next day the Matai steamed over to the east coast of Coromandel Peninsula to deal with a drifting mine reported by the fishing launch Margaret. At daybreak on 8 July the mine was found close inshore off Tepaki Point, whence it was towed by the Matai well clear of the land and sunk in deep water by rifle fire.
More mines were swept outside Maro Tiri during the next few days. On 12 July a ship was sighted to the eastward of the Poor Knights Islands steering a ‘most erratic course in the general direction of the flotilla and the centre of the minefield.’ She was the Panamanian steamer Nortun. The Matai had some difficulty in persuading the master of his danger, but she was finally directed into the swept channel.
By 18 July the total number of mines swept since 13 June had risen to seventy-one, and the senior officer reported that he considered the area from the mainland to a line running north-by-east from a position approximately four and three-quarter miles northwest from Moko Hinau light to be clear of mines. The Naval Board congratulated the officers and ratings of the flotilla on the excellent manner in which they had carried out their duties during a strenuous fortnight under adverse conditions.page 182
After a welcome spell of one week in harbour the flotilla sailed from Auckland on 26 July 1941. On the previous day the fishing launch Waimana had reported three drifting mines, which she had marked by dropping a free dan-buoy, between Great Barrier and Little Barrier. These were the first of a crop with which the flotilla had to deal during a week of stormy weather. On the first day out nine drifting mines were sunk in the Cradock Channel. The continuous bad weather prevented sweeping and kept the flotilla searching for drifting mines until 1 August, by which time three more had been found and sunk. Throughout the week radio stations broadcast and the newspapers printed warnings to shipping and, fortunately, there were no casualties.
When sweeping was resumed on 1 August, the senior officer reported that the line of mines appeared to end as the flotilla approached the western Moko Hinau Islands. Actually the line did not end there, but swung away sharply to the north-eastward in the wide arc round the group on which the raider Orion had dropped her mines to avoid being sighted from the islands.1 Sweeping was interrupted again next day while the flotilla went in search of a mine reported off Cuvier Island. The Matai found it fouled among the rocks close inshore, took it in tow, and sank it two miles southeast from the island.
The weather prevented anything but searching sweeps to the westward of Great Barrier Island until the 6th, when operations were resumed in the Cradock Channel approach between Great Barrier Island and the Moko Hinau group. The senior officer reported that the flotilla did much steaming before the line of mines in this area was discovered to run exactly northward. This part of the line was, of course, the south-eastern end of the arc round Moko Hinau. A start was made with clearance sweeping, but bad weather again set in on 10 August and the flotilla returned to harbour.
The total number of mines swept or destroyed by the flotilla up to that time was ninety-one. In addition, reliable reports indicated that four mines had drifted ashore and exploded on Great Barrier and Cuvier Islands between 26 July and 2 August. A Mr Blackwell, of Great Barrier, found a mine off the southern end of the island on 10 August. He moored it in a small cove, whence it was towed to sea next day and destroyed by HM launch Pirate.
1 The exact location of the Hauraki Gulf minefields was not known until July 1945, when the Admiralty sent out photostat copies of the Orion's track chart and mine plan which had been found in the mass of German naval records captured at Wilhelmshaven. See illustrations section following p. 118.
Stormy weather interrupted sweeping during the next week. The Muritai was sent to Auckland on the 26th to land a sick rating from the Gale and for repairs to her windlass. The Matai had to return to harbour next day with a case of acute appendicitis for hospital. There was other sickness of a less serious nature in the flotilla. Long clearance and searching sweeps accounted for two mines north of Cuvier Island on 1 September and the hundredth mine swept by the flotilla was found south-east of that island next day.
Reports of drifting mines sighted by ships long distances from the areas in which they had been laid came in from time to time, and doubtless there were others that escaped observation. On 30 August the coastal vessel Kopara sighted a mine 16 miles northeast from White Island, in the Bay of Plenty. She and the Port Tauranga, which came up about twenty minutes later, shot off all their rifle ammunition without success, but on her return passage from Auckland the Kopara, in company with the Margaret W, found the mine and sank it in a shooting match in which about one hundred rounds were fired. Two other mines sighted far out in the Bay of Plenty were sunk by rifle fire from ships.
After a week at Auckland, the flotilla carried out searching sweeps from Cuvier Island northward to Needles Point, the northern tip of Great Barrier Island, until 16 September 1941, when that stretch of sea was declared free of mines. The Gale and Muritai were then sent to begin cross searches in the Cradock Channel, while the Matai went to Mercury Bay, where a drifting mine had been found by fishermen. She found that they had moored the mine about three miles off Castle Rock in a highly dangerous state, with its mooring spindle half withdrawn. The Matai towed the mine out and sank it some five miles east from Ohena light. During the check search in the Cradock Channel three mines were swept and sunk by rifle fire, well clear of the line which the senior officer thought he had established previously. Because of his uncertainty about the direction in which the mines had been laid in the Moko Hinau sector, he could not guarantee that the area was clear. An intended check sweep north of the Moko Hinau-Maro Tiri line was cancelled because of the difficulty of getting accurate fixes in the prevailing poor visibility, and the flotilla returned to Auckland on 20 September.page 184
Nevertheless, the approaches to the Hauraki Gulf had been rendered reasonably safe for shipping though navigation was restricted to definite swept channels. When operations ceased, the 25th Minesweeping Flotilla had swept 106 mines and 27 had been accounted for in other ways, making a total of 133 out of the 228 laid by the Orion. Many others undoubtedly had sunk or broken away from their moorings and drifted unobserved far out into the open ocean. One was sunk by the Port Line motor-vessel Port Saint John on 16 February 1942 in a position well to the eastward of Great Barrier Island. Two days later another was sunk by the Port Tauranga about seven miles north from Bream Head. On 24 September 1941 the Naval Board sent a message to the 25th Minesweeping Flotilla congratulating it on a ‘very creditable piece of minesweeping, often carried out under very adverse weather conditions. Special credit was due to Coastguard for her part in these operations.’
A few days later the flotilla went south, sweeping off East Cape and calling at Napier on passage to Wellington. From 6 to 9 October the ships carried out a series of sweeps and patrols in the focal area about Farewell Spit, after which a fortnight was spent in intensive sweeping and gunnery exercises in Cook Strait, the port sweepers South Sea and Futurist being temporarily attached to the flotilla during that period. For the remainder of the year the flotilla and port sweepers were engaged in routine duties or refitting.
In January 1941 the Naval Board decided that an officer should be placed in charge of the disposal of all magnetic mines found otherwise than by routine sweeping. Volunteers were called for to form a magnetic mine disposal party at Auckland. Lieutenant W. H. Minchall, RNZNVR, was appointed in charge and four ratings recommended by him were chosen to complete the party.1
1 Lieutenant-Commander Minchall was later appointed Staff Officer Torpedo and Mining (SOTM). Born Christchurch, 5 Jun 1909; electrical engineer; Superintendent, Armament Supply Depot, 1948.
No magnetic mines were ever found in New Zealand, but official anxiety was not unfounded because, in June 1941, the small German auxiliary vessel Adjutant had actually laid twenty magnetic ground mines from the raider Komet in the approaches to Lyttelton and Wellington harbours. This, however, did not become known till after the war when it was revealed by German records. Nevertheless, the mine disposal organisation was justified by its successful handling of a number of German mines of the contact type washed ashore on the coasts of New Zealand. Most of these had drifted across the Tasman Sea after breaking away from the minefields laid in Australian waters by a German raider. Two mines from the Hauraki Gulf field laid by the raider Orion in June 1940 were destroyed, one on the coast of Coromandel Peninsula on 30 January 1941 and the other south of Mangawai harbour, 50 miles north from Auckland, on 4 April 1942.
The first mine from the Australian coast was reported on 18 October 1942 by Mr J. Dawson, master of the fishing vessel Britannia, in Pegasus harbour, Stewart Island. When Lieutenant Neale and a petty officer arrived from Lyttelton, they found that ‘these well-meaning but foolhardy fishermen’ had secured a rope to the mine and dragged it up on the rocks where it was high and dry at low tide. It was a rusty German Y* type mine with all but one of its horns bent or broken off and the mooring wire missing. Before destroying the mine Neale blew a small hole in the shell with a charge of gelignite to see if there were any unusual internal fittings. The master of the Britannia was paid a reward of £5 for finding and reporting the mine.
In November 1942 Lieutenant Neale had to deal with a German mine found by Mr A. Cropp on the beach about three miles from Westport. After blowing a hole in the casing to examine the internal features and removing all seven horns, which were badly bent, he rolled the mine over until the inspection plate was revealed and the positions of the mooring spindle and the switch noted. The detonator and primer were then removed and, finally, the mechanism plate and the explosive charge.
The MDO's procedure was roundly condemned by the SOTM, who remarked that in not one instance had that officer complied with the Admiralty instructions or carried out the orders of his superior officer. The SOTM recommended that Lieutenant Neale be discharged from the service.
In a second report Neale described some interesting technical features of the mine which, he said, had never been active. The page 186 primer, in the ‘safety for laying’ position, and the state of other parts of the mechanism verified this conclusion. In a spirited defence of his actions, Neale pointed out that the SOTM himself had suggested that a hole could be cut in the shell of the mine. Before the horns were removed all the battery leads had been cut, an almost unnecessary precaution in view of the battering the horns had obviously received. Apart from this and other precautions taken, the harmless state of the mine was proved by the fact that it had survived the rolling and battering it had sustained on the beach and the explosion of gelignite on its casing. Neale wound up his defence by quoting a paragraph in the Admiralty instructions which emphasised that the MDO must be allowed some liberty to work according to the circumstances of a particular case and his own judgment. The saving clause said ‘it is not possible to lay down a definite sequence of operations required for rendering a mine safe….’
The means employed by another MDO, Lieutenant MacKay, to render safe a badly damaged mine washed ashore on a reef at Bell Block, New Plymouth, on 26 November 1942 were also condemned by SOTM. In this case the lower horns, including the elbows, had been wrenched off by bumping on the reef, the mooring spindle broken off flush with the gland, and the mine partly flooded. A small hole was blown in the casing and the interior examined for booby traps, etc. The wires from the horns were cut, the primer charge taken out from under the mechanism plate, which was then removed intact, and the detonator destroyed. The mine was demolished by counter-mining.
MacKay, in reply, took his stand on the permissive clause in the Admiralty instructions and the fact that the former SOTM, Lieutenant-Commander Green, RN (who in August 1940 had dismantled the first mine from the Hauraki Gulf field), had stressed the application of scientific principles. MacKay said his every action had been carefully considered and that the whole operation had since been discussed with and approved by the scientific adviser to the Naval Board, Dr Marsden.
1 Lieutenant E. Savage, RN; born England, 13 May 1893; served RN 1914–18 War; Base Torpedo Officer, 1942–45.
In the same month two more mines were found and dismantled on the west coast of the North Island, one about three miles south from Albatross Point at the entrance to Kawhia harbour, and the other on the beach about 12 miles from Ohakea airfield. On 11 January 1943 the motor-vessel Port Tauranga sank a floating mine by rifle fire about 96 miles west from Cape Egmont.
The Deputy Chiefs of Staff Committee decided in January 1943, on the recommendation of SOTM, to reorganise the mine disposal system. Following a course of instruction at the naval mine depot, Auckland, an army officer was to pass on his knowledge to army bomb disposal units so that they could, if necessary, deal with mines. The naval mine disposal organisation was disbanded and the appointments of Lieutenants Dawson, Neale, and MacKay terminated.
A mine found in New Plymouth harbour on 15 February 1943 was dealt with by an army bomb disposal group under the direction of SOTM. Another mine ashore on Muriwai Beach on 16 May 1943 was dismantled by a bomb disposal group under the supervision of Lieutenant Savage. Two other German mines were similarly disposed of in 1943, one on Ruapuke Beach in the Raglan area on the west coast and the other (doubtless from the Hauraki Gulf field) at Kennedy's Bay, Coromandel Peninsula.
During the next five years, five German mines that had drifted across from Australia were found in various places on the west coast of the North Island from as far north as Hokianga to a point near Raglan harbour. All were destroyed, as was one from the Hauraki Gulf field found at Marsden Point, Bream Bay. Besides these, seven British mines of the controlled type were found and demolished in the Bay of Islands from 1947 to the end of January 1951. These were some of those unaccounted for when the controlled minefields in that area were fired in April 1944.