Nekton

Towards the end of the Second World War the allied forces had air supremacy and it was dangerous for German vessels to sail in the Baltic; the reason that the German battle cruiser, 'Nürnberg' was moored in Copenhagen Freeport. The firepower of the cruiser was significant, and should a battle take place in Copenhagen, the cruiser could prove a serious threat to the members of the Danish resistance movement and others who were to fight one last battle against the German occupying power.

The Resistance therefore decided that the, 'Nürnberg' should be disabled. At first a sabotage action was carried out by placing explosives in a tunnel beneath the quay opposite 'Nürnberg' with the intention of causing coal loading cranes working at the quay to tumble down on to the vessel. The explosion succeeded, but the cranes did not tumble down, and although the cruiser was damaged, it was still operational.

After this incident the Germans moved the cruiser and had it closely guarded both on deck and on the quay. Heavy searchlights were placed to light up the, Nürnberg and the surrounding water, so that attacks from the sea could be discovered. The Resistance discussed a possible attack underwater. Such an operation would require a diver to disable the most watched object of sabotage at that time in Denmark.

After The Royal Danish Navy had sunk their own vessels, (on the 29 August 1943) in order to prevent the vessels from falling into enemy hands, German troops took over the Naval Station Holmen. The Royal Danish Navy Diving School could not continue their work at the Naval Station Holmen, but as the school also trained civilians, it was allowed to continue operating from its base in Tuborg Harbour.

At the time when BOPA was looking for a diver, a diving team of 14 young men was being trained at the Diving School. One of these was   26 years   old, Artillery Mate, Henry Chirholm, from Hørret near Aarhus. Henry   Chirholm   was a   member   of the resistance   group   8 Ø,   which    primarily consisted of personnel from the Navy, and was involved in illegal weapons transport. BOPA's choice fell on Chirholm. Lighthouse keeper Vestbo contacted Chirholm - who agreed   to   carry    out   the   task - and preparations began.

It would not be possible to use an air hose because   the   bubbles   would   reveal the diver's presence and the noise from the air pump could be heard from far away. The Navy   Diving School   had a   Dräger self-
contained diving apparatus, type DM20, and at   the naval station Holmen a two-bolt helmet had been manufactured suitable for use with this apparatus.

On the 15 May 1945, ten days after the German troops had capitulated in Denmark, the sabotage group BOPA (Borgerlige Partisaner - Civil Partisans) held a press conference in the Otto Mønsted Building in Copenhagen. At this press conference several of BOPA's latest sabotage actions were discussed. At this occasion the public was for the first time told about a bold sabotage action to destroy the German battle cruiser, 'Nürnberg', that, at the end of the war, was moored in Copenhagen Port.

The operation involved a diver placing a bomb under the cruiser. The bomb, however, did not explode. The diver was Artillery Mate, Henry Chirholm, who, at the press conference, gave a detailed account of the operation. Although this operation was only one out of many being discussed at the press conference, (and irrespective of the fact that it was not carried out successfully) the operation made such a great impression on the journalist covering the press conference for newspaper, "Jyllandsposten", that more than half of the article was devoted to it. The article was entitled, "The battle cruiser Nürnberg was to be bombed in Copenhagen Port". This operation was certainly a feat beyond the ordinary.

The DM20 is a rebreather working on pure oxygen and emitting a small amount of bubbles that were quickly absorbed in the water. The apparatus was, therefore, ideal for the purpose. For removal of the carbon dioxide from the diver's exhalation the apparatus was equipped with an interchangeable cartridge of carbon dioxide absorbent. It was apparently impossible to procure a cartridge of optimum size, and they had to make do with a cartridge with a working time of one hour. This was considered sufficient. Besides the oxygen cylinders for breathing, the apparatus was also equipped with two small oxygen cylinders in the breast weight. By opening these bottles the diver's buoyancy could be increased, and bring him to the surface.

At the Navy Diving School, Chirholm was trained in the use of the standard diving equipment with air hose connection and in the use of the Dräger DM20. He received a quick instruction in the handling of the bomb, and learned how to activate the time pencils of the explosive charges.

On the morning of 24 April, 1945, Mr. Vestbo contacted marine engineer, N. Juul, at the Navy Diving School and informed him of the operation. Vestbo also told him that one of the students of the diving school, Henry Chirholm, had agreed to place the bomb under the cruiser Nürnberg. N. Juul approved the plan.

It was decided to moor a boat approx. 200 metres from the cruiser. At night the diver would walk on the bottom of the dock and place a bomb containing 100 kg of explosives beneath the cruiser. As the operation was to take place in complete darkness, it was necessary to be able to lead the diver back to the starting point using a thin lifeline. Lighthouse keeper Vestbo had borrowed a boat from the Port Authorities and, to give the venture an official and trustworthy appearance, had procured some Harbour Police uniforms.

The operation was to be carried out that same night, and the final preparations were begun. A 200-metres long, tarred line was borrowed from the marine research ship "Biologen", moored in Tuborg Harbour. The compressed-oxygen cylinders were filled at the Fire-fighting Service's, Smoke Diver Instruction Centre, at Enghavevej.

It was important that the Navy Diving School would not be involved, in case the operation failed, and the equipment fell into German hands. It was therefore agreed that, later in the day, BOPA would arrange a pretended robbery of the Navy Diving School, during which the selected diving gear would be "stolen". When, later that afternoon, the lorry drove up to the Navy Diving School, the "stolen" equipment was willingly loaded aboard and the lorry then headed towards the Port Authorities' motor-boat, at Bodenhoffs Plads. The equipment was placed in the boat where the bomb, consisting of 100 kg explosives in a bag, was already waiting. On that same afternoon all of the parties involved met in Vesbo's apartment for a final briefing.

Chirholm arrived at Bodenhoffs Plads at six o'clock. There were 5 men: Chirholm, Vestbo, the Port Authorities' second diver, Stoker Blitz, from the Navy Diving School and another assistant. Before Chirholm departed for the boat, he called his father in Hørret, near Aarhus, in order to say goodbye in case the worst should happen. Chirholm, however, did not reveal anything about the operation to his father.

Immediately after six o'clock the group sailed towards the Freeport. They had to be in place before eight o'clock, as the harbour would be closed at that time. Right on time, the group moored next to two icebreakers, DFDS's "Bryderen", and the Port Authorities', "Vædderen", in the same northern dock as Nürnberg and only 200 metres from the cruiser.

Shortly after their arrival, German seamen from the, Nürnberg visited the boat. The Danish group fed them with cigarettes and the German seamen did not leave until it was time for them to be back on board the, Nürnberg at ten o'clock.

The time pencils now had to be prepared. This work took place onboard "Vædderen". The time pencils consisted of small explosives that would explode shortly after the pencils had been activated. Time pencils were available with different delays, and those for this operation had a delay of 12 hours. The activation takes place by flattening one end of the pencil, thereby breaking a glass ampoule containing acid. The acid then runs along a metal wire, keeping back a pre-stressed firing pin. When the acid has eaten the wire, the firing pin is released and activates a percussion cap emitting a fire flash into the detonator, which explodes. The pencil is placed in the explosives, which explodes together with the pencil.

However, the time pencils are not functional under water, and in order to overcome this the group provided the pencils with rubber caps to prevent sea water penetrating and ruining them. This work was quite difficult, especially as it was carried out by the light from a candle. Ten to twelve pencils were made ready.

During the work the group needed a pair of tongs. One of the assistants was sent down to the small boat for the necessary tools. Shortly after a voice shouted, "Halt" from the quay. A German patrol had seen the man and wanted to know, what he was doing at the quay at that late hour? Chirholm had also heard the cry. He blew out the candle and hurried onto the quay, fearing that the Germans would come on board. "Noch ein", was shouted in the dark, and Chirholm was required to also raise his hands. Vestbo had also heard that something was wrong. He quickly arrived and explained to the German patrol that the group was from the Port Authority, and had been ordered to check on the sabotage watch on board the icebreakers. When the Danes discovered that no watchmen had arrived, they decided to take over the next watch. The German patrol accepted their story and wished them a "good watch". The fact was that normally there would not be any watchmen on board the icebreakers.

This incident had, however, upset the group. If the bomb and the diving equipment had been discovered, they would have faced a potentially lethal situation. The group talked about what they should do, and were about to give up on the plan until Vestbo's arguments in favour of continuing managed to win them over.

At midnight they were ready with the bomb and time pencils, but, as the night was still young, they waited for two hours before hauling the boat in between the stems of the icebreakers. The boat was partially hidden and, from the, Nürnberg, it was impossible to see what was going on. They started to dress Chirholm in his equipment; first the diving suit, then the breastplate and helmet. Finally the DM20 was installed and connected to the helmet. The breast weight with the small cylinders was hung onto, Chirholm and connected to his helmet and then he put on the brass boots. By 3 a.m. everything was ready. The bomb was lowered down over the side of the boat. Chirholm, descended after it, sliding down the line towards the explosive charge. Standing on the bottom of the dock, seven-metres below the surface, in total darkness and with the lifeline wrapped around his wrist, he took the bomb in his arms and began walking towards Nürnberg.

The bomb was naturally very heavy and unmanageable, and Chirholm sank into the mud up to his knees. After struggling towards the cruiser, he realised that it was easier to walk sideways and draw the bomb jerkily over the bottom, almost losing control as it slipped away. The outlet valve on the diving suit was partially closed, providing slight buoy-
ancy, and Chirholm clung to the bomb for fear that he would otherwise be carried to the surface. Neither did he dare open the valve because of the risk of his exhaust bubbles being seen by lookouts on the surface and his presence revealed.

In the total darkness, Chirholm found it difficult to maintain direction. However, he found the sloping edge up to the quay and followed this. Suddenly he was unable to proceed. He had walked into a bunch of steel wires, and he, the bomb and the lifeline had become entangled in them. He broke into a cold sweat, but managing to remain calm untangled himself, a struggle that disoriented him. He was almost about to give up, when he suddenly saw light in front of him from the searchlights placed round Nürnberg.

He remembered the exact placing of the searchlights and counted them off until he was under the foremost gun turret. The cruiser was lying low in the water and there was just over a metre between the bottom of the dock and the hull of the cruiser. Being now under the ship, he adjusted his outlet-valve to become negatively buoyant. As the seabed rose towards the quay, he tried to place the bomb there, where it would be closest to the bottom of the cruiser, but the bomb slipped down. Instead he chose to place the bomb on the other side of the cruiser - towards the inner harbour.

He assumed that the explosive power was sufficient to strike through the water. The time pencils were placed in a little bag around his neck. One by one he broke the glass ampoules and placed the pencils into the bag with the explosives. When he had finished the work, he followed the lifeline back towards the waiting boat. After a while the line went upright through the water, and he knew then that he was right under the boat. He opened the suit inflation cylinders in the breast weight, but the buoyancy took over completely and with a crash his helmet hit the bottom of the boat. Luckily the German watchmen failed to hear anything.

Chirholm was undressed and all of the diving apparatus and
suit stowed away. The group waited the rest of the night
and at dawn the boat sailed towards Bodenhoff Plads,
stopping on the way to store the diving equipment in a
shed belonging to the Port Authority, at Nyhayn, and to
offload three of the men, including Chirholm. This proved a
wise decision, as a German patrol was waiting for the boat,
when it arrived back at Bodenhoffs Plads.

The Germans thought that the boat had been on an illegal
trip to Sweden, but the two remaining men explained that
they were sabotage watchmen from the icebreaker
"Vædderen". To verify their story, they suggested that the
Germans contact the cruiser Nürnberg. The Germans
believed the two men and left again.

A few days before the operation, Chirholm had only just succeeded in hiding some weapons in a shaft when he was contacted and questioned by the German authorities. He dared not go home. Instead, he went to a coffee shop and sat there half asleep, until late in the afternoon when he drove to the news reporter Kaj Christiansen, at "Det Kæmpende Danmarks Radiostudie" (the broadcast studio of the fighting Denmark) at Amager, where he intended to record a report of the operation for later broadcast by the BBC.

As soon as the bomb had exploded, the recording was to be sent to London via Sweden. Chirholm was very tired and was almost falling asleep during the recording, in which he read from a manuscript written to disguise any incriminating facts. (The manuscript stated that a boat had been under requisition, that naval uniforms had been used, and that the diving equipment was "one brought from England to such purpose".)

The recording begins with, "The person speaking is the man who sank the German cruiser Nürnberg in Copenhagen. This recording was made several hours before the explosion took place, immediately after the explosives was placed ....." However, this was not, what happened. They waited several hours but the expected explosion failed to happen.

The operation took place on the night between the 24 and 25 April 1945. On the 26 April 1945 - the day after Chirholm had made the recording in "Den Kæmpende Danmarks Radiostudie" - he was to take his examination at the Naval Diving School. He passed and the prescribed picture of all of the divers was taken outside the Naval Diving School.

As the operation had failed, the five men immediately started working on a new bomb. Whether water had penetrated into the time pencils, or whether something else had caused the malfunction, would probably remain a mystery. The new bomb was built in a watertight iron container, and the explosive was linked to a timer in the container with a delay of only two hours. A carbon dioxide absorbent cartridge with an operating time of two hours was procured. Everything was thus ready for a new attempt when the German troops capitulated on the 5 May 1945.

However, Chirholm was not finished with Nürnberg. The day after the press conference, in Otto Mønsteds Building, Chirholm - now officially a Navy diver - was tasked with removing the bomb from under the cruiser. This work involved the use of standard diving equipment. When, however, Nürnberg's German captain saw that a diver was to be sent down under his ship, he feared that it might be, "post-sabotaged". He ordered the diver up again, threatening to cut the air hose if his order was ignored. Chirholm was recalled. A Danish Naval Officer wearing an English uniform explained to Nürnberg's captain, what was about to happen, and that he had to cooperate. The captain asked for permission to send a German diver down with Chirholm. This was agreed to and working together, the two divers retrieved the bomb from under the cruiser and brought it back to the surface.

Nürnberg survived the war and was later delivered to the Russian Navy, where it sailed under the name "Admiral Makarow".

Diving equipment, lifeline and the second bomb were exhibited at "Frimurerlogen" (Masonic Lodge) at Østerbro, Copenhagen at the big Resistance Exhibition in July-August 1945.

In recognition of his contribution during the occupation, Chirholm was appointed Quartermaster Third Class and after the Liberation, in 1945, continued his work in the Navy. During his work as diver he was part of a team that cleared Aarhus Port of unexploded ordnance. This ammunition had been scattered all over the port and the nearby part of the city on the 4th July, 1944, when a German barge loaded with ammunition had blown up.

Chirholm continued his career in the Navy and by the time of his retirement, in 1979, had been promoted to Lieutenant-Commander. Chirholm died in 1998.

The author gives warm thanks to: Ebba Chirholm; retired commodore, Per Wessel-Tolvig; news reporter, Otto Ludwig: Commander Senior Grade Løje, of the Naval College; Director of the Museum "Frihedsmuseet" (Museum of Independence") Henrik Lundbak; Leif Kourdahl, Copenhagen Port; and retired Commander Jørgen Strange Lorensen for their invaluable assistance in elaborating and detailing this operation which is to be considered unique.