At the dawn of the 20th century, the submarine was firmly establishing itself within the world’s navies and the Royal Navy began to seriously look at its future applications. In 1905, a committee was set up to finalise the specifications for the next class of British submarine which would be significantly larger than the C-class boats which were then just entering service. While the C-class and the classes before it were short ranged vessels primarily operated in the coastal and harbour protection role, the new class would be the first British submarines designed for a more offensive role requiring greater endurance to conduct patrols at sea.
The resulting D-class submarine was one of the most influential designs in the history of the submarine service incorporating numerous innovations that would be carried on in later classes. It was obvious from the very start that the new class of submarine was going to be significantly bigger than the types then being fielded in order to carry sufficient fuel and provisions for its longer ranged mission. They would also have to take greater consideration in to crew comfort and accommodation than previous classes. This saw the new design eventually swell to over twice the displacement of the C-class coming in at 483 tons on the surface and 595 submerged.
The shape of the new sub would also be came radically different compared to the C-class with the fitting of ballast tanks mounted externally along the pressure hull, a feature that would continue until the Oberon-class launched in 1960. These had the advantage of offering a significant increase in reserve buoyancy that made the submarine easier to manoeuvre and safer to operate in unsettled waters. It also freed up considerably more space inside the pressure hull for fuel and supplies. Another feature included in the design aimed at increasing stability was the fitting of hydroplanes on the forward half of the hull as well as the rear. These had been introduced on the C-class but unlike the earlier type they were positioned so that they remained submerged even when the submarine was cruising on the surface while the aft hydroplane was much further forward due to the unusual shape of the external ballast tanks. The angle of rise and dive angles were set at 50 degrees with the forward hydroplane and 70 degrees in the rear.
Perhaps the biggest departure for British submarine design that the D-class undertook was the adoption of a diesel-fuelled engine for cruising on the surface. This offered numerous advantages over the previous petrol-powered types including importantly for its envisioned mission, greater economy. It was also considerably safer since it was found that explosive fumes often built up in the pumps when using petrol engines. The French Navy had launched the world’s first diesel-powered submarine, the Aigrette, the same year the D-class committee met, proving the concept worked although there were some misgivings especially concerning reliability. The two diesel engines were 600hp units developed by Vickers and each drove their own propellers making the D-class the first British twin-screw submarine type. For propulsion underwater the diesels were cut off and power was provided by a 410kw electric motor.
The D-class had a comparatively impressive range of around 2,500 nautical miles making it a truly ocean-going warship while it could cruise at an economical 5 knots submerged for 45 nautical miles. The committee had demanded that the submarines be capable of around 13 knots on the surface and while it was reported that some of the class could on occasion exceed this figure they generally didn’t travel faster than 11 knots. They were designed for a top speed of 10 knots submerged but the actual speed was closer to 9 although it was rare for them to operate at such speeds due to the significant drain on the batteries this would incur.
Primary armament consisted of two forward 18-inch torpedoes mounted in tubes located vertically on top of one another and with a single reload available for each. The tubes were covered by a one-piece external cap designed to be rotated through 90 degrees to reveal them when it came time to fire. The size of the D-class led some on the design committee to raise concerns that it would not be manoeuvrable enough to escape attack by an enemy vessel and so provision was made for an aft torpedo tube that could be used to launch a torpedo at a pursuing attacker. Unlike the earlier coastal types which could signal the shore with lamps or semaphore, the sea-going nature of the D-class made wireless a requirement from the start and as such it was the first British submarine to be designed with the capability. The aerial was mounted in the coning tower and was extended when riding on the surface but unfortunately was quite short ranged.
So many innovations were being incorporated in to this new design that the committee demanded that the construction of the first-of-class be undertaken by Vickers at Barrow-in-Furness under a veil of total secrecy. The building where HMS D1 was laid down on May 14th 1907 was therefore heavily guarded and all workers sworn to secrecy. The naval race with the Kaiser’s Germany was now in full swing and Germany was building their own submarines starting with the SM U-1 based on the Karp-class designed by Spaniard Raimondo Lorenzo d’Equevilley Montjustin for the Imperial Russian Navy. While inferior to the D-class, the U-1 was an impressive start for the Germans when it was compared to the previous British classes. Further east, the Russians began construction of the Akula as HMS D1 neared completion in 1907 but both these designs were still inferior to the British sub.
D1 was launched at Barrow-in-Furness on May 16th 1918, a year and two days after she was laid down, in a secret ceremony where the only invited guests were a handful of officers from the depot ship HMS Mercury. The submarine was formally commissioned in to the Royal Navy in September 1909 by which time work had started on HMS D2 and HMS D3 at Barrow. On May 3rd 1910, D1 received a new commander in Lieutenant Noel F. Laurence (later Admiral Laurence) who commanded the submarine through that year’s annual naval exercise. The exercise was the chance to get some invaluable experience of the new type engaged in operations similar to what it might experience in war. After loading supplies and fuel in Portsmouth, D1 slipped out of harbour and transited to its operating area off the west coast of Scotland completely undetected by the British Home Fleet. The submarine then conducted a three-day patrol simulating two attacks on British cruisers before putting back to port. Key to remaining undetected was D1’s battery capacity which allowed it to remain submerged during the bulk of daylight hours (in winter the D-class was found that it could remain submerged throughout the fewer daylight hours.)
This highly successful exercise was unfortunately marred by repeated troubles with the revolutionary diesel engines. The fact that D1 had two diesel engines meaning there was always a spare to fall back on was viewed as positively as possible by its supporters but it was clear Vickers had to address this problem if the D-class was to be a success. Despite grand ambitions for a fleet of 18 D-class vessels, the orders was scaled back to ten to allow Vickers time to remedy the reliability issues with the diesels so that these could be implemented on the recently laid down D4, D5, D6, D7 and D8. The latter two vessels in the class were constructed at Chatham Royal Dockyard in Kent and were followed by HMS D9 and D10. During this time, the D-class would find itself receiving yet another first when D4 was completed with a 12-pounder quick firing deck gun and while this would not be fitted to any other members of the class, deck guns would remain on British designs until after World War II.
As experience on HMS D1 and D2 filtered back, a series of recommendations for improvements were submitted and began to be incorporated in HMS D9 and D10. These improvements became so extensive and included greater armament, increased displacement and improved engines that they became a new class entirely. As such D9 and D10 became the first of the new E-class submarines which would serve with great distinction during the Great War however they would also scupper plans for anymore D-class boats. HMS D6 would be the final D-class to be commissioned (April 19th 1912) while D8 was built to a marginally different configuration incorporating redesigned hydroplanes that were all set at 50 degrees for changing depth as opposed to the 50/70 split in the previous vessels. Along with the E-class fleet, the eight D-class boats formed the backbone of the Royal Navy’s patrol submarine force upon the outbreak of war in August 1914.
On August 28th 1914, the Royal Navy met the German Navy in their first major engagement of the war at the First Battle of the Heligoland Bight. The battle took place in the south-eastern North Sea after a British force attacked German patrols off the north-west German coast. Although entirely a surface action, British submarines did play their part and among them was HMS D2 and D8 who were tasked with patrolling the mouth to the River Ems in north-west Germany to block any German reinforcements that may attempt to enter the battle.
Nearly two months later, D8 was sent to shadow the German hospital ship Ophelia which was reportedly looking for survivors from German torpedo boats destroyed in an engagement with HMS Undaunted. The British had become suspicious of the hospital ship because of the amount of radio communication it was making with the German Admiralty and when her crew spotted the British submarine’s periscope they quickly changed course and headed for home even though they were protected under the articles of war which both sides respected in the early months. The M-class destroyer HMS Meteor was sent to inspect the ship under international law and observed her commanding officer throwing secret documents overboard as it approached. The British decided to seize the vessel as a war prize believing it had been spying on British warships thus invalidating its hospital ship status. The British renamed the ship SS Huntley and used it for transporting fuel from Portishead to Boulogne before it was sunk by UB-10 on December 21st 1915.
The class would suffer its first combat loss on November 3rd 1914. D5 was sailing near South Cross Buoy off Great Yarmouth in pursuit of German Admiral Franz von Hipper’s battlecruisers that had raided Yarmouth the day before when it struck a mine laid by the SMS Stralsund. There were only five survivors including Lieutenant Commander Godfrey Herbert who had been in command. Almost three weeks later on November 23rd 1914, D2’s commanding officer Lieutenant Commander Arthur Jameson was washed overboard while the submarine was charging its batteries on the surface. The submarine was then put under the command of Lieutenant Commander Clement Head but his captaincy would be shortlived for on November 25th, just two days after Jameson’s death, D2 was spotted by a German patrol boat on the surface off Borkum which proceeded to ram the British vessel. The submarine quickly sank taking Head and his entire crew of 25 with it.
Along with the E-class fleet, the D-class spent much of the early war years patrolling the Heligoland Bight as part of the British effort to contain the German Navy in port. On June 15th 1915, HMS D4 under the command of Lieutenant Commander John R. G. Moncreiffe stumbled across the unfortunate German netlayer Bielefeld that had ran aground and was being assisted by a German destroyer. Seizing the opportunity, Moncreiffe attacked the destroyer with a single torpedo which unfortunately missed and alerted the Germans to D4’s presence. The destroyer powered up and went in pursuit of the submarine in the extremely shallow water attempting to ram its coning tower that was only just below the surface. Luckily for Moncreiffe and his crew, he eventually managed to evade the destroyer and return to the position of the Bielefeld where they sank the German ship before escaping out to sea.
On August 13th 1917, D6 under the command of Commander William Richardson took part in an effort to lure out German U-boats using a decoy sailing vessel, HMS Prize so-named because she was actually a German topsail schooner captured in the English Channel mere hours after the war began. During the patrol, the two British vessels encountered the U-Boat UB-48 which exchanged gunfire with Prize before disappearing. Later that night close to midnight, D6 was on the surface when they observed Prize explode from a torpedo hit from UB-48 which had returned under the cover of darkness before escaping again. Prize sank with all hands.
On September 12th 1917, D7 under the command of Lieutenant Oswald E. Hallifax was cruising off the coast of Northern Ireland when he and his men spotted the German U-boat U-45. U-45’s war up to that point had been a successful one having sunk 45,622 tons of allied shipping. Hallifax dispatched a torpedo at the U-boat which struck the rear of U-45 as its crew attempted to dive to safety. U-45 sank killing all but two of its crew who were rescued by D7 and taken prisoner.
Tragedy was narrowly averted on February 10th 1918 when D7 was mistakenly depth charged by the M-class destroyer HMS Pelican. Now under the command of Lieutenant George Tweedy, D7 managed to surface and show her flag to the Pelican before any serious damage was done. Not as lucky however was D3 which on March 12th 1918, found itself the focus of attention from French airship AT-0 off Fecamp in the English Channel which mistook the identification rockets the British crew released for being German. The French airship dropped a series of bombs on the British submarine which sent it under the waves. Survivors of the attack managed to escape the doomed submarine and it was only when the French airmen heard them speaking English did they realise their mistake. Efforts to rescue the men proved to be in vain and they had drowned by the time help arrived.
D4 would add another U-boat to the D-class’ list of victims on May 12th 1918 when under the command of Lieutenant Claud Barry, it attacked and sank UB-72 in the English Channel south of Weymouth. The U-boat had been in service with the Germans for just eight months but accounted for sinking over 10,000 tons of allied shipping. Only three of the crew survived the sinking.
A month later on June 24th 1918, the D-class fleet would suffer its last wartime loss when D6 was attacked by UB-73 with a torpedo from a range of just 80 meters. UB-73’s torpedo passed under D6 and exploded throwing a column of water 30-40 feet into the air. At first it appeared D6 was unscathed but approximately half a minute later the front of the British submarine pitched down abruptly and it sank soon afterwards. Only two of D6’s crew survived the sinking and were taken prisoner by the Germans. When these men were questioned over the sinking after the war, the British Admiralty determined that the torpedo must have employed a magnetic pistol; a device used to trigger the warhead by detecting the magnetic field around a metal object such as a ship. UB-73 would survive the war to be surrendered to the French.
As 1918 drew on, the surviving four D-class vessels were becoming increasingly obsolete compared to the newer types then being fielded by the Royal Navy. When it was decided to conduct experiments in to new ways to detect a submerged submarine such as with piezoelectric hydrophones dipped in to the sea from airships (a precursor to modern ASW helicopters), the 10-year old D1 was chosen to be deliberately sunk off Dartmouth harbour. The submarine was sunk to a depth of 25 fathoms (150 feet) on October 23rd 1918 for the trials.
The remaining three submarines were briefly retained by the Royal Navy after the war but seldom went to sea or even had a permanent crew assigned. D4, D7 and D8 were then decommissioned in 1919 before being sold for scrap in December 1921 to H. Pounds based in Portsmouth. Despite their problematic birth, the D-class can be considered a success in their own right. However, their contribution to the development of British submarines and their operation cannot be overstated and would prove the genesis from which nearly every major British submarine class was derived until the nuclear age.