At U 1.16 on 14 October 1939 the British battleship HMS Royal Oak was torpedoed whilst in the protected fleet anchorage of Scapa Flow. Within 15 minutes the veteran of Jutland had gone down in only 13 fathoms but taking with her 833 of her crew. An outstanding coup, the sinking marked the highpoint of the brief career of Gunther Prien; commander of the U.47.

Prien was very much a product of the despair that was the lot of the Germany of the 1920s. At this time he was a youth living in Leipzig with his mother, who eked out a meagre living by selling lace and the odd picture that she painted. Though living far from the sea, he thought of little else; there was, in any case, scant hope of employment in his home town. With his savings earned as a guide at the annual trade fair, he paid to go to the Seaman s College at Finkenwerder to start studies for the master s certificate of which he dreamt. Following initial training, he signed on in a square rigger as a 'Moses', or ship's boy, making a round voyage to the Gulf of Mexico only to be wrecked outside Dublin. Though arriving back in Hamburg a survivor, he discovered that he was in debt to the company to the tune of 5.'10 marks for 'slops' received!

Going into steam, he stayed in the American trades and succeeded in becoming a fourth officer at the age of 21. Disillusion came only three years later when he passed for master but, instead of a ship's bridge, he found only the queue at the assistance board. The humiliation and frustration of useless unemployment, living on handouts of a few marks per week, made him join the National Socialists. Like so many of his generation, he saw in them the only force capable of restoring Germany to purpose and position.

After a spell in the voluntary labour corps, he joined the renascent Kriegsmarine, entering the U-boat training school in Kiel early in 1933. It took him little more than five years to qualify for command and he was rewarded with the U-42, a type VIIB boat being completed by the Germaniawerft in Kiel. She was commissioned into the 7th Submarine Flotilla whose distinguish mark, or Wappen, painted on the side of each conning tower, was a laughing bull.

With war a certainty, the German naval staff sailed 14 U-boats to North Atlantic stations in mid-August 1939; five, including Prien s boat, were from the 7th Flotilla. The war was only two days old when he accounted for his first British merchantman, the Bosnia; by his recall two days later he had added two more. He was already 8,000 gross registered tons toward the record he sought.

It was at the beginning of October that this promising commander was summoned to a conference at which was outlined an audacious plan to penetrate the British naval anchorage at Scapa Flow. Donitz himself had worked it out and, asked his opinion, Prien thought the scheme feasible. He was promptly given the assignment, sailing on 8 October. In appalling weather he took until 13 October to reach the

Orkneys, spending the day laying quietly on the bottom. After darkness had fallen, Prien surfaced to find calm conditions with a slight swell. Despite the lack of moon, however, the veil of the night was shot unpredictably with the multi-coloured shifting curtains of the Northern Lights. While these would assist him in his imminent problem of forcing an entry to the Flow they could also betray him to watchful eyes. Fortunately, for Prien, there were neither eyes nor radar.

Scapa Flow was, indeed, a poor abandoned sort of place compared with its heyday 20 years before, when it had harboured most of the Grand Fleet. Its defences were run down, and pre-war plans to upgrade them were as yet unexecuted. So poor were the defences that the Home Fleet had been long billeted on Loch

Aerial reconnaissance had suggested that this channel, though encumbered by a boom and four rotting blockships, could be negotiated at high water, though only experiment could tell. The submarine shouldered her way through, scraping both beach and barrier. Boldness paid off and, running free, the U-47 found the net barrier beyond of small consequence. With diesels murmuring from the open hatch behind them, the bridge watch stared into the shifting gloom of the wide Flow that was opening up ahead. Initially, there was nothing to be made out then, to starboard, close under the hills of Mainland, could be seen the massive tophamper of a battleship. Beyond her was another. Prien identified them as HMS Repulse and an 'R' class battleship, and swung U-47 around to close.

ln fact, the ships were the Royal! Oak lying outside the old seaplane carrier Pegasus.

The battleship belonged to the 2nd Battle Squadron, which had just completed an abortive search for the marauding German battlecruiser Gneisenau. Where the remainder of the force had returned to Loch Ewe, however, the Royal Oak and her escort, which had been covering the neighbouring Fair Isle Channel, had berthed at Scapa.

Prien calmly reversed his boat and loosed his single stern tube. Again no result and, incredibly, no apparent alarm. Labouring mightily the crew reloaded and a further salvo of three was unleashed. Only two hit, but it was more than enough, the old ship flooding rapidly. In 13 minutes her remains joined those of the German High Seas Fleet just 8 km (5 miles) to the west.

With the Flow now alive with small craft, Prien blasted back the way that he had come, just able to keep steerage way in the roaring tide under Lamb Holm. Less some more paintwork, he was in open water again by 02.15. Returning the 'hero of Scapa Flow', he was received by the Fuhrer himself and awarded the Knight's Cross of the Iron Cross.

Faulty torpedoes were to dog Prien in the Norwegian campaign from April 1940, during which he missed a cruiser and transports at anchor, plus the battleship HMS Warspite. In the June, the so-called 'Group Prien' was formed with U-4'1 and six others. The group operated successfully in the Western Approaches, accounting for 32 merchantmen of about 175, 000 gross registered tons, of which the leader s personal contribution amounted to eight ships of about 51,000 gross registered tons. This total included the ironic and controversial sinking of the ex-cruise liner ~aran Dora Star, whose heavy passenger list comprised mainly Axis nationals en route to internment in Canada.

Using the effective tactic of entering a convoy on the surface at night, possible until the general fitting of radar to escorts, Prien sank four out of the five ships lost by the Halifax-UK convoy SC 2 in August 1940. In the October, he sighted HX 79, vectored in five other U-boats and mounted a co-ordinated onslaught that accounted for 14 ships, three to Prien.

On 6 March 1941 Prien located the westbound OB 293 and brought in four other boats. The convoy was stoutly defended, losing four ships at an initial cost to the Germans of one U-boat sunk and one severely damaged. Prien hung on, determined to exact full measure. Using his surface speed and the cover of rain squalls, he kept the convoy in sight but neglected to watch his flanks. The veteran destroyer HMS Wolverine surprised him, forced

him down and sank him with all hands. It was dawn on 8 March 1941.

Beside the Royal Oak, Gunther Prien's personal score included 30 merchant ships of about 165,000 gross registered tons. His loss was admitted by the German high command a fortnight later, together with the posthumous award of the Oak Leaves to his Knight's Cross.

Strangely, after three months when not a single U-boat had been sunk, the Germans lost four in March 1941. Two of the others also were commanded by 'aces', Kretschmer's U-99 and Schepke's U-100. Able skippers such as these had exploited the early weaknesses of the convoy system. With their loss and the continually improving escort situation, the Battle of the Atlantic turned a significant corner in the long struggle to Allied victory.

'The havoc wrought among the convoys by the U-boat aces was out of all proportion to their number: in the infamous assault on convoy SC7  on 18 October 1940, Otto Kretschmer's U-99 inflicted more casualties than the other seven submarines that took part in the battle, the captain and his crew returning to a hero's welcome at their base at Lorient. This attack, a classic success for Admiral Donitz and his U-boat commanders, originated when U-93 made a general signal giving the position, course and speed of a large convoy it had spotted. In accordance with U-boat tactical doctrine, U-93 endeavoured to shadow the convoy while all other U-boats within range converged on the area. The convoy managed to shake off U-93, only to be spotted by U-48 on the afternoon of 17I October; but by intercepting signal traffic the British knew SC 7 was being followed and the convoy made several violent course alterations, and U-48 lost contact too. Donitz promptly ordered his U-boats to deploy into an 'interception stripe' across the probable course of the convoy. SC 7 eventually brushed the northern edge of the line, and as darkness fell the wolfpack pounced: 17 ships were sunk in a night of desperate fighting.

The aces ignored the procedures they had learned before the war and instead closed to attack on the surface. Kretschmei s favourite attacking position was from the dark side of a convoy so that the target ships were silhouetted against the moon, but if the night was too dark then he approached from windward so that the enemy watch was squinting against the wind and spray.

While many U-boats still made orthodox submerged attacks from outside the escort screen, U-99 weaved among the columns of hapless merchantmen, sending ship after ship to the bottom. Kretschmer commanded that only he could order a crash dive, being firmly convinced that safety lay on the surface. However imprecise, Asdic could pinpoint submerged U-boats for a potentially lethal depth-charging. Time and time again, Kretschmer evaded escorts with his high surface speed, quite prepared to fight his way out rather than submerge. The eventual fate of U-99 was to prove him right.

On 16 March 1941, U-99 joined in another wolfpack attack, slipping past the escorts at dusk and sinking four tankers and two freighters by 3 am. It was her fourth battle in as many weeks, and signalled the end of the patrol. Low on fuel, she set course for home, her captain going below to compose his report to Lorient. But the watch was not alert, and when two destroyers suddenly loomed out of the darkness a junior officer panicked and ordered a crash dive. Kretschmei s worst fears were then realized as U-99 was located by Asdic and pounded with depth charges. Her lights went out and she plunged out of control well below the maximum safe depth. Ankle deep in water and with the hull groaning under the pressure, Kretschmer had no choice but to surface and surrender.