ANTISUBMARINE DEFENCES IN SOUTH AFRICA
In 1939 the ports of the Union were defended by batteries manned from the Permanent Force Artillery and in September 1939 Cape Town was covered by two short-range 9.2 inch guns (22000 yard range), and Simonstown by two of similar type and two 9.2 inch guns of improved design (33000 yard range). At Capetown three long-range 9.2s were planned for Robben Island to guard the approaches to Table Bay but these were not in position until November 1940.  At Durban there were two semi-obsolete 6-inch guns, at Port Elizabeth and Walvis Bay two 5-inch, and at East London two 6-inch guns - all short range and mounted on field carriages. In terms of Naval firepower, by 1939 the Union of South Africa had no significant naval force. Prior to WW1 (in 1910, when the four colonies united) both the Cape and Natal had possessed active divisions of the Royal Naval Volunteer Reserve, which were amalgamated by the Defence Act of 191 to form the South African Division - Royal Navy Volunteer Reserve (RNVR).

Naval Training
During WW1, South Africans served in ships of the RN all over the world, guarded docks and Admiralty property and manned the coastal defences of Durban. In the early 1920s the RNVR (SA) trained aboard the ship General Botha  at Simonstown. In 1922 the Union Government acquired two minesweeping trawlers and a survey ship and established the SA Naval Service, only to see it abandoned in 1932 by the 'Gold Standard' financial crisis. By September 1939 the RNVR (SA) had a strength of 70 officers and 900 men spread over the training bases of Cape Town, Durban, Port Elizabeth and East London. These officers and men trained on a part-time basis of about two weeks per year aboard on one of the RN ships. The RNVR (SA) was expected to man shipping control and examination services at Union Ports should war break out. Their duties also included provision of signalmen for shore stations, guns' crews in merchant ships, and manning of 30 auxiliary minesweepers and four armed merchant cruisers.

Antisubmarine defences
As for antisubmarine defences, in March 1939, the Union Government issued a memorandum about procedures on the outbreak of war. Thirty six trawlers and whalers would be equipped as auxiliary minesweepers, and fifteen as antisubmarine vessels. Most of the ratings and many of the officers needed were to come from the RNVR (SA), the balance from RN Reserves. When war did come the RNVR (SA) was overwhelmed with volunteers but had no facilities for training them. Training was to be very much on-the-job. By the second week of September 1939, Naval Officers-in-Charge were installed, with staffs, at the four principal commercial ports as previously named. Officers and men were also supplied for Port War Signal Stations (PWSS), Examination Services, and Naval Control Services. The first three minesweepers were ready by 15th September 1939 and by the end of December there were 15, manned by RNVR (SA) members. It was soon discovered that for legal reasons a new command (to be called the Seaward Defence Force) had to be set up. Enough members of the RNVR (SA) volunteered to transfer that the new command was off-and-running by 15th January 1940. Fortunately, for South Africa, there was a breathing space before the need for defence would become urgent, but not without some scares beforehand.

First attacks
By March 1940 disguised German raiders were making their way to the Cape. First was Atlantis which sailed on 31 March 1940, soon followed by Orion (6 April), Widder (6 May), Thor (6 June), Pinguin (15 June) and Komet (3 July). The Admiralty knew them as Raiders C, A, D, E, F and B respectively. On 15th May 1940 the Seaward Defence Force had it's first success of the war when the South African minesweeper MV Aristea detected and exploded a mine laid by German raider Atlantis 6 miles off Cape Agulhas - a major shipping route. The following map shows the location:



Harbour Defences
With the likelihood of a dramatic increase in shipping arrivals and enemy activity to South Africa in late 1942, the Union Government stepped up its antisubmarine program. The laying of the Cape Town antisubmarine indicator loop system began on 11 July 1942 but was held up by bad weather and not completed until 20th November that year. The defences consisted of four loops each about 6 km long which enclosed the whole of Table Bay, including Robben Island where the "loop hut" (control station) was located. The loops were laid on the sea bed from Melkbosstrand in the North around Robben Island and down to Clifton. It was a good choice for a secure navy base. It had served as a hospital for leprosy patients, and the mentally and chronically ill (1846-1931). In the 1840s, Robben Island was chosen for a hospital because it was both secure (isolating dangerous cases) and healthy (providing a good environment for cure). During this time, political and common-law prisoners were still kept on the Island. The map below shows the approximate positions of the Cape Town indicator loops in Table Bay. The loop cable consists of a single core of 7-strand copper wire insulated with rubber and tarred hemp and loaded with a layer of lead to make it heavy and less susceptible to movement in the currents. The cable is armoured with 24 steel wires and waterproofed in tarred hemp. Diagrams and photos can be seen on my loop cables webpage. The tail cables (shown in light blue) are steel-armoured and multicored but not lead-loaded. Loop and Tail cables would have been recovered at the end of the war but usually only 50-70% of the cable is recovered as much of it gets buried under silt or is weakened by chaffing on the seabed or rocks.

The loop defences at Durban were the next to be undertaken. Seven loops, again each 6 km long were laid, but because only one cable-laying vessel was available, this was not completed until April 1943. The control hut was located at Umhlanga Rocks, 7 miles North of Durban Bluff.
 

Umhlanga Rocks Lighthouse - today	Robben Island lighthouse and WW2 barracks - today

To defend the inner harbours of Durban and Cape Town against midget submarines, frogmen and similar attackers, depth-charge throwers were mounted at the entrances. These were activated on information received from the indicator loop officers. Later in the war, the depth-charge throwers relied on signals from the harbour defence Asdics (HDAs). Similar defences (indicator loops, HDAs) were to be installed at Port Elizabeth and East London in 1944 although it appears the Port Elizabeth loop defences may have been reallocated to Walvis Bay (a part of South Africa during WW2 but now in Namibia) . The entrance to the major port of Saldanha Bay (110 km NW of Cape Town) had no indicator loops but was guarded by a controlled minefield completed in April 1943. This minefield consisted of eight rows of mines, each surrounded by a 'mine loop' (similar to an indicator loop) and a few hundred metres to the ocean side were eight  'guard loops' ready to make the first detection of any submarine. A personal account of life with the SA Naval Force during WW2 is provided in Lt Andrew Murray McGregor's fascinating memoirs, an extract of which appears below.

Further attacks
The first real threat by German U-Boats came in August 1942 when Admiral Donitz ordered four U-Boats (and a U-Boat oil tanker) to proceed to Cape Town but also ordered them to attack any allied shipping they may come across. These U-Boats had been successfully operating off the US East Coast but better A/S defences by the US Navy (including USN indicator loop defences at a dozen or more ports) reduced the U-Boats' effectiveness and better hunting grounds were sought. Admiral Donitz thus turned his attention back to the Atlantic.

Conclusion
Naval operations in the southern oceans adjoining South Africa ended in early 1945. Within 1000 miles of the Union the losses were one allied warship (the Dutch submarine depot ship Colombia) and damage to the British depot ship Hecla. Merchant losses from submarines amounted to 133 ships (117 sailing independently, 15 in convoy, and 1 straggler) - 750,000 tons. Raiders accounted for 20 ships and mines for 2 ships. The strategic significance of the Cape has been recognised by historians (see "War in the Southern Oceans 1939-45" by L. C. F. Turner & J. E. Betzler, OUP, Cape Town, 1961); the Cape route was the only link between Britain and India and the far East for almost three years, and its severance would have brought about collapse of the Allied effort in the Middle East. That the allied losses were not greater around the Cape is regarded as a tribute to the fine qualities of the men and women who fought for the cause.

The extract below comes from the memoirs of the late Andrew Murray McGregor (1908-2002), prepared as a webpage by his son Tony to whom I am grateful for his permission to reproduce a small part.  His father Andrew Murray McGregor was born in Worcester, Cape Province, on 26 May 1908, when the Province was still a colony of Great Britain. He died in 2002, having lived through two World Wars, the unification of the four British colonies into the Union of South Africa, the exit of apartheid South Africa from the British Commonwealth of Nations in 1961, when it became a republic, and its increasing isolation from the rest of the world, and then the birth of a new, non-racial democratic country after April 1994, which once again joined the British Commonwealth of Nations.

Early 1942.....

After a safe but boring journey to Cape Town I reported to Naval HQ .........

[F]our of us “oldies” were sent to the new anti-submarine base on Robben Island where we immediately began a new course in electrics, as the introduction to our anti-submarine course. Thereafter we learnt about the “loops” that had been laid in a huge semi-circle from Melkbos Strand in the North to Clifton in the West, all circling Robben Island. Each loop (there were four of them) consisted of three lengths of cable, each about five miles long, all parallel with each other and joined at the ends. From one end of each loop there was a thinner cable to connect the loop to the instruments in our base, which was called the Naval Sub-Depot, Robben Island, so that its real function could be kept secret. For the same reason the buildings in which the instruments were set up and the other buildings which housed all the naval personnel were built among trees and bushes to hide them from the sea or the air. A thin steel lattice mast with steps on it was used by the people on look-out duty.

To begin with the erection, fitting out and staffing of the “NS-D,RI” was in the hands of RNR or RNVR officers and ratings. I was in the first class of SANF officers to do the Anti-Submarine Fixed Defences course here. The course lasted some eight weeks, if my memory is correct, and there were about a dozen or twenty in the course. Two of our number failed the final tests and were returned to ‘General Service’; four of us were kept on Robben Island and the other successful candidates sent to start new A/S F/D bases or to join existing bases in the other seaports around our coast.

The RNVR officer in charge of all this land-borne anti-submarine work, whose title was “Anti-Submarine Fixed Defences, South Atlantic” and who was thus always referred to as “ASFIDOSA”, received an order from the Admiralty in London to scrap the plan for the erection of an anti-submarine fixed-defences base in Port Elizabeth and instead to do so in Walvis Bay. The reason was that the Japanese had begun to make attacks in Madagascar and had even sent a large submarine which carried a seaplane to make a scouting trip to Durban, during which the seaplane flew over the harbour and the town, causing the first air raid alarm signal there. This alarmed the authorities in South Africa and also in London, as it was feared that that island and the south-eastern part of South Africa might be the region for the next Japanese attack on the Allies, so it was decided to scrap the idea of building a new A/S F/D base in Port Elizabeth and instead to set it up in Walvis Bay. I was chosen to do this, so I had to go by train from Cape Town to Port Elizabeth and to see to the embarkation of all the A/S F/D gear, which had been landed there but not yet used, into a Danish cargo ship, the MS Tureby, a 4 500-tonner which had already taken aboard much cargo destined for Britain.

The easiest part of this job was to put aboard the cartons in which the A/S detection instruments were kept. As they were very much “official secrets” it was decided to put them into the cabin destined for me, so that I could lock them into it and keep the key myself. Incidentally, they filled the cabin so completely that I could not use it myself, thus I had to sleep on a cushioned bunk in the officers’ dining saloon and use the captain’s bathroom which was next to it. The biggest and most tiring part of the operation was to deal with the undersea cable, some 50 miles of it, which weighed over 4 tons per mile. The core of this cable was the usual copper wire for taking the current, but this had to be securely insulated from the sea water by a covering of thick rubber and, as that had to be protected from breaking, this was all covered with a thick layer of steel wires and that by a coating of canvas which had been water proofed by being soaked in tar for a long time! All this meant that the cable had a diameter of about three inches. We had to pay the cable out from its huge coil on the dockside, a coil that had to have an inside diameter of at least 20 feet, to prevent the cable’s being bent sharply enough to break it. The diameter of the coil on the outside was about 40 feet and its height over 8 feet. We had to lift the cable and uncoil every foot of it, bring it over to the top of No 3 hatch and re-coil it in the hold. We had to work night and day without stopping for 12 days, with several different groups of labourers. When all the cable had been transferred from the coil on shore to the coil in the ship’s hold there was another task to see to, the building of a timber “wall” all round the coiled cable. The outer sides of this wall being held in place by balks of timber fixed between them and the ship’s steel sides.

When all this had been done, the Tureby’s captain got his orders from SANOIC, the SA Navy’s senior officer in Port Elizabeth, to join a coastal convoy that was to pass Port Elizabeth on its voyage from Durban to Cape Town. This we did. The merchant ships in the convoy were drawn up in three rows of five ships each, with a destroyer zig-zagging in front of them, a corvette doing the same right aft and a whale catcher turned into a submarine chaser on each broadside. On the first evening out, as I was at dinner with Captain Lohse, his chief officer and the chief engineer, all very friendly Danes, we were nearly thrown off our chairs by a tremendous shaking of the ship followed by a tremendous noise. We all rushed up to the top of the superstructure and, looking aft, saw the corvette and one of the whale catchers going round in circles and dropping depth charges, with the destroyer rushing round from the front of the convoy to join in the fun. The merchant ships were ordered to keep going at full speed. We soon left our escort behind but, about half an hour later, they caught up with us, the corvette signalling to us by lamp, “Sorry, just a school of porpoises.” We were all very sorry for the poor porpoises but glad to know that there was not just then any danger from U-boats. Three days later we arrived in Cape Town, where all the ships filled up with extra cargo and with fuel for the long haul across the Atlantic.

As I had done well in the A/S courses that we had received and it was known at HQ that I was by profession a teacher I was told that I was to be an instructor-officer to various groups that were sent o Robben Island, our Sub-Depot being an instructional as well as an operational base. My first effort in this duty was to take a group of about a dozen SANF lieutenants and sub-lieutenants in the eight week’s A/S F/D course. Then I had a six-week’s course for Leading Seamen, a shortened, more practical course and later about three more officers’ courses. During this time most of the RNVR officers had been returned to the RN and then Lieut. Perkins left Robben Island to become A/S F/D OSA in charge of all the A/S F/D stations round our coast. His promotion led to mine as, in addition to being the chief Instruction Officer on the Island I had to take over as Commanding Officer, S/D R/I.