Friday 21 October 2016

The salvaging and afterlife of minelayer UC-5

A blog on Tuesday 3 November 2015 described the horrific sinking of the hospital ship Anglia close to English south-coast in 1915. She was a victim of a submarine-laid mine, a weapon that was to prove a deadly menace during World War 1. Such mines not only inflicted direct losses it but were also effective in restricting or closing harbour approaches and shipping lanes for long periods once their presence was detected. The German submarine responsible for the Anglia was the small UC-5, a craft specially designed for minelaying. Her operational career was a short one – from late July 1915 until April 1916, a mere none months – but in this time she was responsible for sinking a total of 29 ships, with a total gross tonnage of 36,288 tons. Few warships have ever been so cost-effective in terms of investment needed to sink a ton of shipping.

Artist's impression of Anglia's final plunge, November 17th 1915
The fifteen submarines of the UC I class displaced 168 tons on the surface and were a mere 111-feet long. Single-shafted, with a 90-hp diesel, and a 175-hp electric motor, they were slow – 6.5 knots on the surface and 5.5 knots submerged – and this was hardly a disadvantage since it enhanced the stealth with which their operations must be conducted. With a crew of 15, they carried no torpedoes and their purpose was to drop the twelve 39-inch diameter mines that they carried in six tubes inclined slightly off vertical. Their short range was not a disadvantage when they operated along the British coast from bases in Belgium.  

Contemporary cutaway drawing of UC-5. Note mines in inclined tubes ahead of the conning tower.
UC-5 was to be the first of these German vessels to pass safely through the British defences – including minefields – that protected the Dover Straits and to reach the wider waters of the English Channel beyond. It was here that UC-5’s mines were to claim the Anglia as well as many other victims. It was however further north, on the approaches to the British base at Harwich, from which light forces operated in the Southern North Sea, that the UC-5’s luck ran out. The attraction of the area was obvious – twelve mines laid in the approaches to Harwich would have had a high likelihood of claiming a warship victim. The complication was however shallow water offshore – the Shipwash Shoal lay some twelve miles to the north-east of Harwich and it was across this that the UC-5’s commander, Oberleutant Ulrich Mohrbutte intended to make his approach. It was in the course of doing so on April 27th 1916 that the UC-5 grounded as the tide dropped.

Unable to break free, and with a clear possibility of capture, Mohrbutter ordered charts and papers to be destroyed and for scuttling charges to be put in place. He sent a radio signal to the German base at Zeebrugge to give news of his plight and this was picked up by the British. The Royal Navy destroyer Firedrake was accordingly sent to investigate, arriving in early afternoon. As she approached the stranded submarine – her own draught was shallower – the German crew were seen to be standing on the deck and holding up their hands. When Firedrake drew still nearer, the Germans jumped into the water and were soon picked up by boats dropped by the destroyer.

It was thought that the entire German crew had been rescued when one last man was seen emerging from below, shouting and waving his hands frantically, and then jumping overboard. He was picked up and shortly afterwards several explosions racked the stranded submarine, and brown smoke poured from her conning-tower. The scuttling charges had been fired. The craft settled on the shoal beneath but the mines on board – all twelve – did not explode.

UC-5 in British hands, afloat after salvage and repair
Once satisfied that no further explosions were likely, Firedrake’s Torpedo-Lieutenant Quentin Paterson and two other officers went across. Even though damaged the UC-5 was a valuable prize, the first German U-boat to be captured virtually intact and one that was likely to reveal significant technical information. She was however sufficiently holed to make flotation at high tide and towing to Harwich impossible. Measures were accordingly put in hand to mobilise divers and salvage equipment to recover her. Before these arrived Paterson made a full examination that revealed that though ten of the mines were still secure in their tubes, two had been dropped – as part of the scuttling procedure – and now lay loose at the bottom of the tubes and resting on the sand beneath. The danger was that movement of the submarine’s hull could be enough to detonate them. All salvage efforts had therefore to be delayed until the mines were made safe.

Lieutenant Paterson himself, together with two others, one a diver, undertook this very hazardous work. The ten mines still in the tubes were disarmed by the removal of the acid detonation tubes from the contact horns but it was impossible to do this with the lower mines, which therefore remained active. It was found that the two projecting mines could not be drawn back into the tubes, nor could they be disarmed, so they were secured where they were with cables in such a way as to ensure that they could not drop further. The danger remained however of them being detonated by the hull bumping on the sand when it was time to move it.

UC-5 being transported in sections through Central Park, New York
Responsibility for the salvage was assigned to Commodore Sir Frederic William Young (1859-1927), a naval-reserve officer who in civilian life was the nation’s, and perhaps the world’s, best respected salvage expert. Working now in the open sea, in the middle of a war zone, and with the two unexploded mines a constant danger, the recovery of the UC-5 was to prove one of his greatest challenges. The UC-5 was by now sinking ever deeper into the sand as the tides washed around her. A lighter was brought alongside and the hull was lashed to it at four places with heavy cables – passing these under the hull by water-jetting must have been a terrifying ordeal for the divers who did so. The first attempt at lifting as the tide rose (and as the lighter was deballasted) ended in failure. The cables parted and the hull dropped back on the seabed, luckily without setting off the mines. The process had to start over, this time with yet heavier cables and a larger lighter to which the UC-5’s hull was secured at low water. The lighter's side tanks nearer the submarine were pumped dry and her outer tanks were filled with water so as to act as a counterweight. This time the UC-5 was raised safely. She was towed into Harwich and placed in a floating dock in which the two projecting mines were safely removed. The entire operation had taken 27 days.

UC-5 in Central Park in 1918 - a focus for sale of War Bonds
 The UC-5 was to have a strange afterlife. Examined meticulously to understand her working, she was subsequently patched up and taken to London where she was put on display – an amazing sight since submarines represented cutting-edge technology and the vast majority of the population had never seen one. When the United States entered the war a year later the submarine was cut into sections and sent to New York. She was reassembled in Central Park and there also she became an object of wonder, all the more so since it was outrage at German unrestricted submarine warfare that had drawn the United States into the conflict. 

And the heroes of this epic? Paterson was awarded the DSC (Distinguished Service Cross) and his diver the CSM (Conspicuous Gallantry Medal). They were hard earned.

Britannia’s Shark by Antoine Vanner

The dawn of the Submarine Age ...

1881 and the power of the British Empire seems unchallengeable.

But now a group of revolutionaries threaten the economic basis of that power. Their weapon is the invention of a naïve genius, their sense of grievance is implacable and their leader is already proven in the crucible of war. Protected by powerful political and business interests, conventional British military or naval power cannot touch them. A daring act of piracy draws the ambitious British naval officer, Nicholas Dawlish, and his wife into this deadly maelstrom. Amid the wealth and squalor of America’s Gilded Age, and on a fever-ridden island ruled by savage tyranny success – and survival –will demand making some very strange alliances...

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