1. Distant Patrol Areas: January to May 1943.
The North American coast was left unguarded temporarily while the attempt was being made to sink U.S. shipping between Newfoundland and UK by U-boats in groups. At the end of February orders were issued to 5 U-boats for special task Seewolf, later identified as a patrol of U.S. waters. However, information on UGS 6, presumably derived from decryption, resulted in cancellation of the orders, and the U-boats joined group Unverzagt for the convoy operation. By April it appeared that it might be profitable to attack U.S. convoys shortly after they had left U.S. ports. Three U-boats operated between Bermuda and Halifax during April, with discouraging results. In payment for the one ship sunk, one U-boat was sunk, an uneven exchange from the German point of view. But this set-back did not deter the assignment of even more U-boats to the area, and 5 more appeared off our coast in May. However, the same story was repeated. The same U-boat which sank the ship in April sank another in May, and again a U-boat was eliminated in payment. A U-boat for a ship was the score for June as well. The strength of antisubmarine defenses in North American waters was evident, and this fact, plus the absence of any but neutral traffic in some of the attack areas to which U-boats had been assigned, was reported to COMSUBs with each transmission. The U-boats were held down, and their movements restricted to such an extent, particularly between New York and Halifax, that the Commanders gloomily reported that operations were impossible. To add to U-boat difficulties, many promising attacks were foiled by the extremely bad weather.
The results of the campaign in the Caribbean were a little more impressive. Ten ships were sunk by the 7 subs which occupied attack areas in the Caribbean from January to May. The concentration reached its height in March and April, when 5 U-boats were in the area and 4 ships were sunk each month. Only 6 of the 7 U-boats managed to return to France, as one was sunk in March just after starting for home. By the middle of April, the Caribbean was free of U-boats and remained so throughout May. U.S. antisubmarine defenses were evident in
the pessimistic reports sent to COMSUBs. Operations against convoys in the Trinidad area were declared to be impossible because of the constant aircraft patrol, accurate attacks by aircraft even without searchlights, and a "new kind of radar," against which German search receivers seemed useless. Several of the U-boats were forced to remain submerged and were pursued, heavily attacked and damaged by sea and aircraft patrol.
The South American coast from the Guianas to Brazil was the scene of considerable activity. Eight U-boats operated in that area and sank 13 ships. Two convoys were hit heavily in January and March. Two U-boats were sunk in January, one by convoy escorts, and the other by USN aircraft a few days after it had sunk a neutral ship. Another was sunk in May while unsuccessfully pursuing a convoy. Other subs were damaged by depth charge attacks and forced away from targets by aircraft patrol which was described as "constant," "systematic" and "strong." "Pursuit," said one Commander, "is without prospects."
Only one ship was sunk off West African coast before the serious effort against shipping in that area was begun in April. Possibly discouraged by the report sent back by the one sub off Freetown in January, the Germans gave this area a wide berth for the next two months. The Commander reported that he had been forced underwater by persistent aircraft attacks, bombs, searchlights and radar; his sub had been "starved out" by systematic aircraft patrol and had no freedom of movement. He was severely damaged by depth charge attack, which caused him to lose great quantities of fuel. The comments of the 4 U-boats that operated in the Dakar-Freetown-Monrovia area in April and May were less forcibly expressed, but intimated that the antisubmarine defenses had not weakened. They, however, were able to sink 10 ships in that period. One sub was sunk, probably after having been refueled in the South Atlantic in May.
By far the most rewarding distant patrol area for U-boats during the period from January to May was the Capetown area. Here group Seehund operated from February to April, sinking 22 ships. The Seehund U-boats did not remain in the Atlantic waters around Capetown, but operated also in the southern Indian Ocean as far north as Inhambane. Although their record of ships sunk were good, and no sub was sunk in the Capetown area, they did not find themselves entirely unhindered by
antisubmarine defenses. From time to time they were forced to submerge by strong day aircraft patrol, and radar from land and night aircraft prevented them from getting in close to the main harbor. The good coordination of land radar and sea activity was especially apparent. No sub seems to have been damaged by aircraft attack from February to April, but the 5 U-boats which occupied this area in May were not so fortunate. They sank 7 ships, but 2 of their number were attacked and damaged by aircraft, and one was sunk when it was half-way home.
U-boats enroute to the Indian Ocean attack areas also sank some ships in the Capetown area, taking advantage of favorable opportunities as they presented themselves.
The shipping loss figures presented above were compiled from a consideration of German traffic claims and information available from Allied sources.
2. Refuelings: January to May 1943.
Although the fleet of U-boat tankers was at its greatest strength at the time of the great North Atlantic offensive in the spring of 1943, it was nonetheless inadequate for the sizable task at hand. The refueling system was strained to the limit and operated at great expense because of the necessity for simultaneous supply of North Atlantic groups, concentrations on the Gibraltar lane, and U-boats operating in distant waters.
The deployment of refuelers during this period reflects the general pattern of the Atlantic offensive. The scale of group warfare against the North Atlantic convoys shows a gradual increase which reaches its peak in March, the month of greatest success for the U-boat fleet; then a withdrawal in April; and finally a last, all out attempt in May. The scale of refueling rendezvous was, of necessity, the same. In January and April there were two major refueling rendezvous in the North Atlantic, while in March there were five, and in May, seven. With about 70% of the operational U-boat fleet diverted to these vital convoy lanes, it was necessary to use 90% (8 out of 9) of the active supply boats at one time or another in order to keep the U-boats at sea as long as possible.
In March came also the end of a two months' concentration in force on the Gibraltar convoy lane, necessitating the diversion of three refuelers to provision these subs for continued operations, or for their return home. Since
more could not be spared from other refueling grounds, inbound and outbound subs had to help out.
These operations against convoys bringing supplies to England, Russia and Africa were of the utmost concern to Germany; hence the U-boats were ordered to operate with no regard for fuel, until they had only 5 cbm left, just enough to get to the refuelers. To insure the provisioning of these subs, the U-tankers were forced to make two cruises in five months, thereby spending much less than the normal two months in port between cruises. The situation became so strained at times that it was necessary to divert a few operational subs from their cruises in order that they might supply the fuel required for the important convoy operations from their own stock.
In addition to the heavy duties in the North Atlantic, four supply boats were required to undertake cruises solely for the purpose of refueling U-boats returning from patrols in distant areas. The supply was still inadequate, however, and several operational subs were forced to share their fuel with returning U-boats. In order to relieve the supply situation, U-boats in distant areas were ordered to discontinue the operations in time to reach France without provisioning, or, in other cases, to take on a bare two weeks' supply. However, the cruise of a supply U-boat in January to the South Atlantic for the purpose of giving maximum fuel advantage of the subs of group Seehund, operating off Capetown, demonstrated the importance still attached to distant operations; for the boat was not available for use in the critical battles in the North Atlantic until May.
The disposition of refuelers during this period was know through radio intelligence, and the advantage of eliminating them was obvious, but unfortunately the physical facilities for doing so were lacking. Not until the late spring of 1943 did U.S. Navy CVE's appear in the Atlantic. By May it became evident that the Atlantic would soon cease to be the untroubled refueling ground it had been.
3. Special Tasks: January to May 1943.
Various special tasks were carried out by 24 U-boats during the first five months of 1943. All of these U-boats performed other more common operations prior to or subsequent to their special tasks. Twenty of them were 500
and 750 tonners, the former normally used for group operations against convoys in the North Atlantic, and the latter for patrols in distant areas. Three combination supply boats and minelayers were employed for both types of operations, and another refueler was given the individual task of reporting the enemy antisubmarine situation in the Denmark Straits on his outward passage from the north. The tasks carried out by the U-boats not especially designed for them were assigned as expediency dictated or adjuncts to the desperate, final spring attack on North Atlantic convoys.
Rendezvous with blockade runners were arranged for 10 U-boats. As the time grew near for the arrival in France of such of these ships as were enroute from the Far East, single U-boats were sent to rendezvous with them and deliver operations orders, instructions, personnel, and to take off mail. As they approached the dangerous waters of the Bay of Biscay, groups of inbound or outbound U-boats in that area were assigned to escort these valuable ships in port. On 20 February, the Herborg being expected, four U-boats were ordered to provide protection for her Biscay cruise. They met the ship, but could not prevent her being sunk on 26 February, after which the U-boats continued their cruises, operating on convoys in the Gibraltar lane. One blockade runner to be met late in March, however, had been scuttled in the South Atlantic two weeks before the proposed rendezvous, and the U-boat concerned went on to meet Irene on 6 April. This accomplished, the U-boat proceeded to his attack area off New York, where he was sunk, and the blockade runner, continuing its trip to France, was also sunk on 10 April, the day after four U-boats had been detailed to provide anti-aircraft protection for her. Having failed in this mission, the U-boats went on to complete their cruises, two of them to the North and South American coasts, where they were both sunk, and the other two to convoy operations.
A U-boat bound for the North American operational area first redezvous'd two blockade runners in the last week of March. One, the Pietro Orseolo, made port in France. The other, Regensburg, was carrying a cargo described by prisoners of war as the most valuable ever carried by a blockade runner. Because of this the U-boat supplied her with special routing orders which were to take her through the Denmark Straits to Germany instead of through the hazardous Biscay waters.
Ironically, the ship was sunk in the very waters which had been considered safe.
The Denmark Straits were investigated for antisubmarine defenses by U-boats coming out of the north in February and March, solely for the purpose of routing blockade runners through waters less perilous than those of the Bay of Biscay. Several U-boats were diverted from the "Rosengarten" passage, between Iceland and Greenland, seldom used as an outbound passage route. Special attention was to be paid to air and sea search groups, and the use made of radar. This intelligence was duly sent back to Germany, and the Regensburg was routed accordingly in the hope of escaping Allied surveillance, with results as described above.
Six U-boats laid mines in February, April, and May. Three were of the 1600 ton supply ship minelaying type, and three were small 500 ton short range operational subs. This type of operation was normal for the former type, but the use of the latter type indicated that all means, however extreme, were being employed to sink Allied ships in the North Atlantic. After their mine laying cruises, one to Halifax and two to Lands End, the 500 tonners had to participate in group operations against convoys. Problems of stowage and refueling are evident in such double purpose cruises and this fact, together with the sacrifice of three supply ships, greatly needed for refueling operations at that time, for one mining operation off Halifax and two off Tangier, emphasizes the demands which were being made on each U-boat to operate to more than maximum capacity.
In January, three agents were sent ashore near Port Etienne, French West Africa, from a U-boat. One returned to the U-boat, but the other two gave themselves up to French police when their means of returning to the U-boat was lost. The U-boat then joined in operations against convoys on the Gibraltar lane.
Another U-boat was given the taxing assignment of pretending to be several U-boats heading for a point in the North Atlantic by transmitting dummy messages, each sent by a different operator, in the faint hope of deceiving the Allies as to the strength of U-boats concentrated at that point.
Automatic weather buoys were set out in the mid-North Atlantic by a U-boat in April, and in the same month, a U-boat filled in time before joining a group by operating in accordance with task "Cruiser," an operation as yet unidentified
4. Independent Patrols in Distant Waters: October 1943 - May 1944.
From October, 1943 to May, 1943, 34 U-boats made independent cruises to distant patrol areas. They were all 750 tonners. In the 8 months of operations, only 28 ships were claimed sunk in all areas. Although only two U-boats were sunk in their attack areas, reports sent home by returning boats give sufficient indication that antisubmarine forces were almost everywhere in evidence. From the Caribbean: "Complete aircraft patrol over Caribbean Sea." From the coast of South America: "Dense aircraft, PT boats with flares, D/C's." From the Halifax area: "Strong day and night aircraft with radar; terror bombs." Surface patrol in some parts of the North American coastal waters and in the Caribbean seems to have been rather weak, and was described as "slight, inexperienced." Also instrumental in reducing the strength of operations off Allied shores was the scarcity of refueling facilities, which caused cruises to be limited to little more than one month.
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