Black May (18 page)

When on 24 March this recommendation was placed on the table by the A.U. Committee for discussion one week hence, the Admiralty found themselves rebuked in their desire to pass from the defensive to the offensive in the U-boat war by going full-bore in the Bay. This was all the more vexing since Slessor’s Command was technically under the operational control of the Admiralty. One week later, however, as shown in chapter 8, Their Lordships would be back with a counter-strike—and the Americans alongside them.

Professor Blackett left the O.R.S. of Coastal in January 1942 to become Chief Advisor on Operational Research (C.A.O.R.) to the Admiralty.
In that capacity he recruited a prestigious scientific team similar to that at Coastal—Evan Williams would follow him to Whitehall in January 1943—and cast his practical intellect across the whole range of naval operations, including, in a notable study, the optimum size of convoys. For years the number of ships in convoy had hovered at around forty-five, though the origin and rationale for that rule could not be found by Blackett. A formation larger than that was assumed to be dangerous, since it presented so many targets.

When in late autumn 1942 Blackett investigated convoy statistics for the two-year period 1941–1942, he was startled to find that convoys averaging thirty-two ships had 2.5 percent losses, but that convoys averaging fifty-four ships suffered only 1.1 percent losses. Those figures offended common sense, and Blackett knew that his team would have to develop convincing reasons to explain them. One reason was readily apparent: while the fifty-four-ship convoy occupied a larger sea area than a thirty-two-ship convoy, the guarded perimeter of the area did not expand by the same proportion. And several weeks of hard analysis produced these findings:

Even with these data in hand, Blackett had difficulty convincing the Naval Staff to enlarge the size of convoys, since the staff worried about the vulnerability of a sixty-ship convoy to frontal attacks, an increasingly
popular U-boat tactic, as well as about communication and control problems. He eventually won them over, however, and the Admiralty, in turn, at the 3 March meeting of the A.U. Committee, gained that body’s approval to start running sixty-or-more-ship convoys on a case-by-case basis, as would be done.
⁵⁹
A sixty-one-ship convoy, HX.231, departed Halifax on 29 March escorted by one frigate (SO), one destroyer, and four corvettes (Escort Group B7; see chapter 4). Helped by a Support Group and Liberators, it arrived at Londonderry 95 percent intact. Blackett wrote later that it was unfortunate he had not appreciated the importance of the convoy size question much earlier than he did. During the preceding year alone 200 ships might have been saved.
⁶⁰

In a report to the A.U. Committee dated 5 February, Blackett threw himself into the defense versus offense debate that was then brewing in all the pertinent Commands. Without taking sides, he presented the “defensive values” of saving ships and the “offensive values” of attacking U-boats. Briefly stated, the defensive value of the surface escorts was found, first, by noting that shipping losses in the North Atlantic during the last six months of 1942 were at a rate of 210 ships per year, while the average number of escorts was 100. Since the statistics showed that the number of ships torpedoed per submarine present in an attack decreased as the escort force increased, and that an increase of the average escort strength from six to nine would be expected to decrease the losses by about 25 percent, had there been an additional 50 escorts available in the time period cited losses should have been reduced by fifty-ships (25 percent). Or, expressed differently, each escort vessel would have saved about one ship a year.

In determining the offensive value of surface escorts, the assumption was made that the sinking of a U-boat saved the shipping it would have sunk in subsequent months. If the escorts sank seven and damaged eight U-boats, and the eight damaged could be considered the equivalent of two additional boats sunk, since the statistics showed that about 0.4 ships were sunk per month by each operational boat, an average of 3.6 ships were saved by the sinking of a U-boat. In their offensive role the 100 escorts saved about 0.7 ships per escort vessel per year. A comparison
of the defensive and offensive numbers gave the edge to the defense. Where aircraft were concerned, Blackett made similar assumptions and calculations. Using air cover over threatened convoys in the period cited, for defensive value, he calculated that each long-range aircraft in its average life of forty sorties saved about thirteen ships by defensive action. By contrast, where aircraft conducted hunting operations independent of convoys, for example, the Bay Offensive and other search and attack sweeps, the offensive value obtained from the maximum number of sorties flown by one aircraft was about three ships saved. Again, the results favored the defense.
⁶¹

All through March and April the defense-offense question was debated at Western Approaches, where there was increasing criticism that the current policy—“The safe and timely arrival of the convoy at its destination is the primary object of the escort”—was insufficiently bold. Even the role of the Support Groups as ancillary to the close escorts was thought by some to be a waste of their aggressive potential. Admiral Horton, whom no one could accuse of lacking in offensive spirit, and who longed for the day when he could simply “attack and kill,” nonetheless approached the question carefully, mulling over what was known of recent enemy contact and behavior.

During April sixteen convoys were attacked and suffered loss, in no case severe, however; the largest number of ships torpedoed in any one convoy was four. Of those, seven were transatlantic convoys (HX.231–234 inclusive, ON.176 and 178, and ONS.3). The typical U-boat Commander still preferred to attack on the surface at night despite the fact that radar and snowflakes (illuminants) had made that a more hazardous action than it was the year before. The U-boats now strove to get ahead of a convoy, apparently so that they could attack submerged if success on the surface seemed unlikely. In making follow-up attacks, U-boats took advantage of the disturbance created by first attacks, and they displayed a tendency to follow one another in from the same direction, from a mile or two back. Boats detected and driven off by the escorts at night frequently made no additional attempts to attack during the remainder of the night; thus, the boats had only to be detected for the battle to be half-won.

With present enemy policy, most attacks developed in front of the beam of the convoy. The U-boats were attacking more eastbound than westbound convoys, no doubt because the latter carried no cargo and were under first-class air protection for the first 600 miles of their run. Their tendency was to operate primarily in the area between 500 and 700 miles to the northeast of Newfoundland, presumably to be outside the range of aircraft based in Iceland and Ireland, air cover from Newfoundland not apparently being much of a concern to them.

Horton then considered various aspects of escort work: Practically every U-boat sunk during the past year was destroyed
prior
to its attack on a convoy, not afterward. U-boats were most effectively dealt with when they were on the surface, now that asdic was no longer the escort’s only weapon; therefore, forcing a U-boat to dive was not always the best policy. Analysis of asdic figures on lost contact for the last six months of 1942 showed that sixty-four percent of boats were at depths of less than 200 feet when lost. And since the morale of the Merchant Navy was showing signs of strain, it was undesirable to use convoy ships as “bait,” that is, to accept the sinking of merchant ships as a way of indicating the presence of a U-boat so that it might be attacked.

With that, however, Horton in effect threw up his hands. None of the recent data were any help in resolving the defense-offense question. To defend or to hunt? He finally decided that the Tactical Policy “must still be the safe and timely arrival of the convoy.” But there was no reason he could not have it both ways. He left the Escort Groups open to “exercise their initiative under all circumstances,” thus giving them authorization to take such offensive action as seemed prudent, necessary, and opportune, while making certain that the convoys under their care were not unduly exposed to enemy attack. “The matter was largely a question of numbers,” he wrote in a signal sent on 27 April to all British and Canadian Escort and Support Groups under CinCWA. “Whatever form of warfare is considered, the question of the strength of the opposing forces must play a very large part in deciding whether an offensive or defensive role can be adopted.”
⁶²
The defense-offense question, then, would not be decided at Derby House. It would be decided at sea.

F
ORTY-THREE MERCHANT SHIPS
that would make up Outward North Atlantic Slow Convoy Five, abbreviated ONS.5 and code-named MARFLEET, assembled for their voyage on 21–22 April. Destination: Halifax, Nova Scotia, with detachments to Boston and New York. Mostly gray in color, their names painted out, they had sailed from five different ports—Milford Haven, Liverpool, the Clyde, Oban, and Londonderry—and now had rendezvoused off a lighthouse-crested rock called Oversay that rises from the sea at the North Channel entrance between northeast Ireland, the southern isle of the Inner Hebrides, and the Mull of Kintyre. There, over a twenty-four-hour period, the convoy Commodore J. Kenneth Brook, R.N.R., formed his charges, three and
four deep, into a broad front of twelve columns. At the center, in column six, Brook stationed himself ahead in the Norwegian ship
Rena,
with only the New York-bound American oiler
Argon
astern.

Most of the ships were elderly tramp steamers. Most were British, but
McKeesport, West Madaket,
and
West Maximus,
as well as
Argon,
were of United States registry;
Bonde, Rena,
and
Fana
were Norwegian;
Berkel
and
Bengkalis
were Dutch;
Agios Georgios
and
Nicolas
were Greek;
Ivan Topic
Yugoslav;
Isabel
Panamanian; and
Bornholm
Danish. Two ships,
McKeesport
and
Dolius
(British), had been with SC.122 when that convoy was savaged by U-boats on 17–20 March. There was not a ship at R/V Oversay that had not sailed in convoy before. The majority were steaming in ballast, bound eventually for North and South American ports where they would load up food, fuel, raw materials, and finished weapons. Seven ships carried coal (“coal out, grain home”), four had general cargoes, and one listed general cargo and clay. Three ships in addition to those at Oversay were to join the formation at sea from Reykjavik, Iceland, on 26 April:
Gudvor, Bosworth,
and the U.S. Navy tanker U.S.S.
Sapelo,
which was returning to the States in ballast. Most of the convoy vessels were Defensively Equipped Merchant Ships (D.E.M.S.) with single four-inch guns manned by Navy and Army gunners. Gross Register Tonnage varied greatly, from tiny
Bonde
at 1,570 tons to the largest freighters at plus or minus 10,000 GRT.

Whatever their size, the merchantmen were expected, once underway, to maintain a speed of seven and a half knots, though their Masters knew, with gale-force seas forecast along the westward course, that was not a likely prospect. The ships’ crews also varied in composition, most of them British Merchant Navy, some U.S. Navy and Merchant Marine, others East Indian or Asian in whole or in part except for officers. Most crew had small canvas “panic bags” for carrying their most valued possessions into the lifeboats, if that became necessary; the Americans’ bags were more the size of railroad luggage.

By 1200
^*
on 22 April this unexceptional, businesslike merchant fleet was formed up at Oversay with 1,000 yards separating the columns and
800 yards between each ship ahead and astern. The entire formation occupied eight and three-quarter square nautical miles. The shepherd, Commodore Brook, had gathered his flock. Now he awaited the sheepdog, who, he hoped, would hold the sea wolves at bay. At 1400 the sheepdog arrived in the person of Commander Peter Gretton, R.N., Senior Officer Escort, aboard the destroyer H.M.S.
Duncan,
accompanied by the frigate H.M.S.
Tay,
the corvettes H.M.S.
Loosestrife, Pink, Snowflake,
and
Sunflower;
two rescue trawlers,
Northern Gem
and
Northern Spray,
and the tanker
British Lady.

Together, the warships made up Escort Group B7, the midocean close escort screen charged with seeing convoy ONS.5 to a “safe and timely arrival” at its assigned destination on the opposite shore.’ A second destroyer, H.M.S.
Vidette,
had been sent ahead to escort the two freighters and the USN tanker from Iceland to a midocean rendezvous with the main body.
Vidette
’s Captain, Lieutenant Raymond S. Hart, R.N., was the only regular officer besides Gretton in the group. Two corvette Captains were Australians, one was Canadian; several officers were New Zealanders.

Thirty-year-old Peter William Gretton was educated at the Dartmouth and Greenwich Royal Navy colleges, and, rather than select a career specialization, which was the usual route to promotion, he chose to remain a general seaman officer, or “salt horse.” In a nod to specialization he learned to fly and amassed fifty hours of solo time, though he pronounced himself “not a good pilot.” In 1936 he earned a Distinguished Service Cross (DSC) leading a landing party at Haifa during the Arab rebellion in Palestine. Three years later, as war with Germany loomed, he did a week’s course in anti-submarine warfare at Portland, H.M.S.
Osprey.
That experience, together with his flying, would give him a leg up in understanding the U-boat war when it came. His hankering had always been for destroyers, and he counted himself lucky to be appointed First Lieutenant of the famous destroyer
Cossack,
on which he served in the Second Battle of Narvik, where he was mentioned in dispatches. In 1941 he received his own destroyer command on
Sabre
, and entered convoy escort duty full-time. Transferred to
command of the destroyer
Wolverine
in 1942, he helped escort the celebrated Malta convoy in August of that year and, while steaming in the Mediterranean at 26 knots, rammed and sank the Italian submarine
Dagabur,
with the loss of all hands, for which action he was awarded the first of three Distinguished Service Orders (DSOs).

During the weeks when the crumpled bows of
Wolverine
underwent repair, Gretton took the anti-submarine warfare course devised by Captain Roberts at the Tactical Unit in Derby House, Liverpool. The schooling was a turning point for Gretton in several ways. First, he learned how unaware he had been of German submarine tactics and of the best means for frustrating them by use of the latest shipborne detection and weapons technology. Under Roberts’s tutelage, he quickly filled in the knowledge gaps.

Above all, Roberts stressed, effective ASW seamanship meant learning how, perhaps for the first time, to
think.
War at sea had changed. Courage and endurance were no longer enough. Victory over the U-boat required the intelligent use of technical aids, particularly HF/DF, 10-centimeter radar, and asdic, in that sequence. Second, Gretton realized at Derby House how much convoy duty had been denigrated by the regular Navy, which esteemed big ship-big gun fleet actions and considered the passive tending of seaborne trade as beneath their dignity, with the result that all the best officers went to the Home and Mediterranean fleets, while the failed careers and incompetents ended up in Western Approaches—with certain very notable exceptions, for example, Captain Frederic John Walker, R.N., and Captain Donald Macintyre, R.N., salt horses like Gretton. There was a desperate need in the Atlantic of more good regulars, he concluded (and when, belatedly, in 1943–44, the Home Fleet regulars realized that the Atlantic was where the war was, they climbed over each other to get Escort Group commands). Third, Gretton determined that if ever he received an Escort Group command of his own, he would bring his regular and reserve officers up to Roberts’s—and now his—exacting high standards.

That brass hat came in December 1942 when he was advanced to command of Escort Group B7, based at Londonderry. There he embarked in the new twin-screw River class frigate
Tay
, while the
destroyer assigned to him, the eleven year-old, 329-foot, D-class flotilla leader H.M.S.
Duncan,
was refitting in Tilbury docks prior to recom-missioning. The B7 Group had just come off a rough convoy engagement in which the Senior Officer Escort (SO) and his ship had been lost, but Gretton found his ships to be “in great heart.” Throughout January, February, and March, a period of expanding U-boat activity, he led them on cross-Atlantic passages that were, ironically, eventful for their lack of U-boat contacts. “For three months the group ran hard but had nothing to show for it but rust,” he wrote later. “We seemed always to steer clear of the wolf packs, which were then at the height of their success.”
²

Aboard
Tay
he had his first sea experience with an HF/DF set. The Type FH3 equipment could identify the general position of a U-boat transmitting to base or to another boat on a high-frequency wave band, even indicate whether the U-boat was near or far. More exact “fixing” of a U-boat’s position required the “cross-cut bearing” provided by a second HF/DF-equipped ship, as
Duncan
would be when recommissioned. Between sailings Gretton worked his officers and technical ratings hard at Londonderry’s asdic and depth charge trainers, radar and HF-DF detection simulators, and the new Night Escort Attack Teacher, where all ranks and ratings who manned detection and communications equipment, the plotting table, or the bridge received intensive and realistic attack drills in nighttime conditions. Time and again they practiced on land the tactical maneuvers they would have to carry out at sea, which bore such code names as Raspberry, Half-Raspberry, Observant, and Artichoke.

Gretton was relentless in the conduct of these exercises and he was quite prepared to sack anyone who flagged in the effort. Among his Captains he had the reputation of an egotist but a gentleman, a hard man but a fair man. “Kindness to incompetents seldom provided a dividend,” he wrote after the war, “whereas severity invariably paid. As [German Field Marshal Erwin] Rommel said, ‘The best form of welfare is hard training.’ … But the sailor will never admit it.”
³
Gretton had no need as yet to purge this group, however, and the men of B7 seemed to have welded into a tautly skilled team.

Group B7 finally got its blooding in early April when it relieved a
Canadian group escorting the fast (nine knots) Convoy HX.231 from New York to the United Kingdom. Entering the mid-Atlantic Air Gap on 4 April, B7 soon had more than enough U-boat contact to make up for its sterile months, as for over four days and nights it battled a pack of fourteen boats.
Tay,
commanded by Lieutenant-Commander Robert Evan Sherwood, R.N.R., made asdic contact with one of them, U-635, and sank her with a well-placed pattern of depth charges. Another boat,
U-632,
had been sunk earlier by a Liberator aircraft from Iceland. And U
-294,
badly damaged by depth charges, was forced to return to base. But six merchantmen were lost in the exchange: three in convoy and three stragglers.

The first loss, that of the British motorship
Shillong,
was the worst for Gretton. Loaded with zinc concentrate and wheat in bulk, the 5,529-GRT vessel sank from view within two minutes of being torpedoed, casting her entire crew into the sea. On her search for the U-boat,
Tay
passed slowly through the bobbing survivors, their life jackets aglow with red lights. Gretton shouted encouragement to them, but knew that pursuing the U-boat was his most urgent duty, lest others be attacked, and that
Tay
must not lie hove to lest a torpedo remove her from the screen. But, as late as 1964, when he wrote about the men he left to die, he called the moment “my most painful memory of the war…. ”
⁴

Finally, a mist descended on the ocean swells and ruined the visibility of the U-boats. On 7 April aircraft roared overhead in great numbers. Eventually, landfall was made off the north coast of Ireland, and B7 reentered its home port at Londonderry. Ninety-five percent of the convoy had come through the pack battle unharmed, and B7 had acquitted itself well in its first real trial of pluck and mind. Gretton was pleased—except with the performance of
Loosestrife,
whose Captain, in his view, had not shaped up to standards, and whom he promptly replaced.

Waiting for Gretton was the recommissioned
Duncan,
which not only gave him a destroyer to go with the frigate
Tay,
but also gave him a second HF/DF set (Type FH4), which made possible cross-cut bearings in combination with
Tay’
s FH3, which alone during HX.231 had proved “worth its weight in gold.”
⁵
Duncan
was also reequipped with the latest asdics, Type 271 10-centimeter radar, and radio transmitters and receivers. On deck she mounted two guns, two torpedoes, and the new forward-firing impact-fused “Hedgehog.” Extra depth charge stowage had been created. His complement of 175 officers and men was unknown and untried, however, and he immediately set them to work jousting with last war-type submarines in the Londonderry exercise area, except on those days when he was asked to review HX.231 with Admiral Horton (CinCWA) in Liverpool, address a large audience of officers on the same operation, and huddle with RAF Coastal Command pilots on how better surface and air escort cooperation might be promoted.

Then came the date, long predetermined, for ONS.5.

As he pulled alongside the Commodore’s ship,
Rena,
Gretton exchanged documents with Brook, whose orders had come from the Trade Division of the Admiralty, and advised him by loud-hailer of the disposition of his forces. Gretton stationed
Duncan
in the center behind
Argon
and formed up the rest of his force on the port bow, beam, and quarter, and on the starboard bow and quarter, with the tanker and rescue trawlers astern. The screen in place, Brook signaled his convoy to gather way on course 280°. Notwithstanding the confidence
B7 had gained from HX.231, Gretton had every reason at this moment to be apprehensive. He was sailing northwestward into what forecasters told him was atrocious weather with gale-force winds. That meant that his convoy ships, light on the water because they were in ballast, would be buffeted about like so many champagne corks, and that would work havoc with stationkeeping, throw some ships out of control, and leave others stragglers. Maintaining seven and a half knots would be impossible under those conditions. Furthermore, their course, northwest to 6
1
°45’
N,
29°II
‘W,
a position east of Ivigtut on Greenland, and thence southwest along the Great Banks of Newfoundland, would engage his fleet with pack ice and bergs.