The loss of U 33 and the wheels of the Enigma code writer
The short combat service time of U 33 was marked by two missions to sea areas around the British Isles and the Gulf of Biscay in 1939. The first mission tasked the U-boat under the command of Kapitänleutnant (= Lieutenant Commander) Hans-Wilhelm von Dresky to an area of operation west of Ireland and in the Gulf of Biscay, where it sank two vessels with a total tonnage of 5.627 GRT. While on its return leg to Wilhelmshaven the U-boat sank the British fishing vessel Caldew by artillery. During the combat patrol U 33 was attacked twice by British aircraft, however, it was able to evade damage by emergency diving maneuvers.
The second mission started on 29 October 1939. This time, the Commanding Officer was tasked to lay a mine barrier in the Bristol Channel. He executed the mine laying operation on 09 November 1939 between 03.15 hrs and 04.28 hrs, delivering a total of 12 mines. After that, U 33 operated between the Hebrides and off North Foreland, where it sank five British fishing vessels by artillery within two days.
On 23 November U 33 met the Dutch freighter Bussum. Desky had tried unsuccessful to stop the ship by flag signaling. He was not aware at this time that the vessel was the former German freighter Borkum, which had been captured by British forces in the North Sea on 18 November. The prize was simply renamed by the British to Bussum and had received Dutch markings, to then being sent to Kirkwall at the Orkney Islands with a British prize crew on board.
When the vessel did not react to the signal from U 33, Dresky stopped it eventually by firing some shells before the bow. Once the vessel suddenly resumed speed again and turned towards the U-boat, Dresky ordered to shell the vessel directly. Several hits were made and the vessel started burning. Now, U 33 submerged for attack and fired three torpedoes, but all missed. The U-boat surfaced again and shelled the vessel again with four rounds right at the waterline. U 33 did believe the vessel would be sinking now when it left the scene of action. However, the British actually managed to bring the Borkum to shore, albeit crippled. The vessel had suffered severe damage and its status was beyond any repair. Consequently, it was put to scrap.
The mine barrier laid by U 33 in Bristol Channel caused the loss of the British 2.473 GRT freighter Stanholm and the British 9.456 GRT oiler Inverdargle. U 33 returned to Wilhelmshaven on 26 November 1939, to start a maintenance period in the Westwerft shipyard.
On 05 February 1940 U 33 left Wilhelmshaven for its third and fatal mission. The BdU (= Flag Officer Submarines) himself had tasked the 42 men of U 33 to a daring mission. Again, it was to lay mines, this time at an important sea line of communication for the British, i.e. the mouth of River Clyde at the Scottish western coast off Glasgow.
The U-boat was heading northbound through the North Sea into the Atlantic Ocean, to then proceed towards the area of operation assigned. The atmosphere on board was intense while the U-boat was passing southbound a severe gale. The crew was well aware what was coming up, when the U-boat reached the outer Clyde in the evening of 11 February 1940. Here, it was the most important anchorage of the Allies at the Eastern side of Atlantic Ocean. Eventually, U 33 penetrated submerged the Clyde around midnight 11 to 12 February 1940. For many sailors on board it was actually some relief as day-long seasickness came to an end which was caused by the permanent rolling in the rough sea state of the Atlantic Ocean.
At the same time, the Royal Navy´s 830 tons minesweeping and anti-submarine vessel HMS Gleaner under the command of Lieutenant Commander Hugh Price was patrolling the area. The area of surveillance assigned was ranging from south of Arran up the northern most point at Pladde lighthouse.
At 02.50 hrs HMS Gleaner established sonar contact to U 33. The British Commanding Officer ordered “Action Stations” for the 80 men strong crew. Within minutes the 4-inch guns and the launchers for the depth charges were manned, the crews ready for combat action. Also, on board U 33 the crew was at full alert enabling Dresky to act fast. Through few steering orders he managed to escape the immediate danger caused by the detection. At the surface, HMS Gleaner now had to commence a nerve racking and long lasting search to regain contact to the target.
Half an hour later, at a moment the British crew on board the Gleaner started to believe to have lost the target for good, the Sonar operator at the Asdic device suddenly called to have regained contact to the German U-boat. The searchlight was activated and its ray immediately caught the spray-like wake behind the U-boat´s periscope and the periscope itself. While HMS Gleaner increased speed the periscope vanished from the surface. At 03.36 hrs the rudder was turned left changing course to starboard to chase the object, with the engine room telegraph set to “Full Ahead”. At 03.40 hrs HMS Gleaner was right on top of the target and the Asdic was firmly hooked on U 33. At 03.53 hrs four depth charges were dropped, and contact was lost consequently during the detonations. Later, the First Watch Officer of U 33, Oberleutnant zur See (= Lieutenant) Karl Vietor remembered that the depth charges had detonated right above the U-boat. All lights on board the U-boat went out, some instruments were damaged and several leakages developed. Emergency lights were switched on. Soon, the pressure air would be consumed to end status. Therefore, the LI (= Chief Engineer), Kapitänleutnant Fritz Schilling, recommended the Commanding Officer to surface – or to initially escape the scene of action with high speed. However, Kapitänleutnant von Dresky decided to put the U-boat idle on the bottom of the ocean. After their rescue, it is reported that the surviving officers of the U-boat criticized that decision. Anyway, what different course of action should Dresky have selected instead: He hardly was able to attack HMS Gleaner, as the bow torpedo tubes of U 33 were loaded with mines, just one torpedo was left in the stern torpedo tube.
At 04.12 hrs HMS Gleaner launched a second attack, this time dropping one depth charge only. A third attack followed at 04.40 hrs dropping a series of five depth charges, set to detonate between 35 meters and 50 meters. Contact was lost again and the Gleaner using its searchlight continued to observe the surface with speed at twelve knots. Suddenly, it was 05.22 hrs, the German U-boat was caught surfaced by the bright searchlight. At once the Gleaner opened fire with its 4 inch gun, ceasing fire after five rounds. HMS Gleaner was preparing for ramming when the British crew observed that the U-boat´s crew had assembled on the upper deck, hands raised in the air. The rudder was put to “hard starboard” to take position parallel to U 33, distance about 250 meters.
Precisely at 05.30 hrs a light explosion did shake the U-boat and sparks were emitted from the conning tower, when the crew already on deck left the U-boat jumping into the cold sea. Later, it became known that the Commanding Officer had ordered to place high explosive charges between the classified equipment on board. Also he had ordered to distribute the wheels of the Enigma code writer among the sailors to drop those when swimming in the sea, if possible as far distant from the U-boat as possible. The water depth at the position of the expected sinking of U 33 was about 55 meters.
In fact, after the explosion the U-boat started sinking at an angle of 40 degrees over the bow, to vanish from the surface almost silently after a few seconds. The port life boats of HMS Gleaner were lowered to water to head for the survivors of U 33. Both starboard life boats could not be released since Gleaner itself was drifting fast towards lee. Also, too much time would be needed to regain enough speed to close to a group of survivors. The sea state was rough and the life boats had enormous problems to gain enough speed against the sea. Eventually the life boats of Gleaner managed to pick up one officer and eight ranks from the U-boat´s crew. Meanwhile, two trawlers has rushed to the scene, with the Floradora rescuing one officer and the Bohemian Girl picking up two officers and eight ranks, sadly two of those died during the return leg of the trawler. Another vessel having rushed to the scene, destroyer HMS Kingston managed to pick up further 22 U-boat sailors, however, just two of those were still alive. With that, only 4 officers and 13 ranks from U 33´s 42 strong crew survived. 25 men died, mainly due to exhaustion and hypothermia, including the Commanding Officer Hans-Wilhelm von Dresky.
The 17 survivors were handed over to the police and transferred further to interrogation and to a PoW camp. The bodies of the dead sailors were given a ceremonial funeral with full military honors at Greenock cemetery. Later, they were re-bedded to the large central German War Cemetery at Cannock Chase in Staffordshire.
Still today, the wreckage of U 33 is located 53 meters deep in the Firth of Clyde 53 meters at position 55° 21,29′ North and 05° 01,41′ West.
Only decades later, after the UK had released formerly classified information, it became known that the British has discovered a total of three wheels of the Enigma code writer in the pockets of the U-boat´s sailors picked up from the sea. Also, the Royal Navy had sent down divers to the wreckage of U 33 which tried to enter the inner U-boat. The diving operations were rather risky because of the strong current in the Clyde. It is not known until today whether anything could be salvaged out of the inner U-boat to be examined afterwards. For sure, the British got hold of three wheels of the Enigma code writer as early as February 1940. This was step one for the UK to decipher German R/T-message traffic, which became one of the key successes in the war at sea 1939-1945.
Text: Hans-Joachim Röll, pictures: German U-boat Museum