HMS D3 – A Case of Mistaken Identity

HMS D3 (

HMS D3 (

The First World War changed the nature of military conflict beyond recognition. Not since the Battle of Agincourt where French Knights in armour found themselves rendered obsolete by new weapons had war been revolutionised so quickly. The new wars being waged under the sea and in the air both came of age and on a handful of occasions these two arenas clashed. Unfortunately this led to tragedy in March 1918.

HMS D3 was commissioned on August 30th 1910 at a time when the infantile Submarine Corps was still considered something of a pirate branch of the Royal Navy being viewed in a similar fashion to how regular servicemen once viewed British privateers. The third of the D-class submarines, an improved version of the previous C-class, HMS D3 operated in northern waters for the bulk of the war helping to enforce the blockade against Germany and contain the Imperial German Navy. Her first taste of combat was anything but glorious however when the submarine fired on another submarine believing it to be a German vessel when in fact it was HMS E48. Fortunately the torpedoes missed but the incident would have ghostly echoes upon the story of HMS D3.

On March 7th 1918 the submarine set off for another war patrol of the English Channel under the command of Lieutenant William McKinstry Heriot-Maitland-Dougall of the Royal Canadian Navy. The situation at sea as well as on land had swung well in favour of the Allies although the German surface fleet remained alive it refusing to come out of port in force for the Royal Navy, now supported by the US Navy, to destroy it. This left the Imperial German Navy’s U-boat fleets to keep the fight alive and they had proven dramatically that they had the power to alter the course of the war first by demonstrating how vulnerable the Royal Navy was to submarines when three Cressey-class cruisers were sunk in a single engagement by just one submarine and then by sinking the liner Lusitania which effectively brought the United States in to the war on the side of Britain and France. U-boats therefore became high priority targets for the anti-submarine forces of the Allies.

The crew of HMS D3 (

The crew of HMS D3 (

After being escorted to the patrol area by a British destroyer so as to allow the submarine to pass through British defences without being mistaken for a German vessel the destroyer turned back for the Isle of Wight leaving D3 to begin hunting for German vessels. A World War One submariner’s life was a tough one even more so than later in the Second World War. Their vessels themselves were just as likely to kill them as the enemy and so just volunteering for the Submarine Corps was an act of courage alone. Even when everything was running smoothly as far as the submarine was concerned life was cramped, uncomfortable and lacking in privacy as the crew almost literally lived on top of one another. Officers and crew transferring from big ships were often amazed at how lax the discipline on submarines were in comparison for there just wasn’t the room for the usual pompous nature of life in the Royal Navy but this in turn bred new types of crew. Submarine crews were tighter teams and the feeling of brotherhood amongst those who served in the underwater branch of the Royal Navy was unparalleled so losses, and there were many, were felt throughout the force.

On March 12th 1918 HMS D3 was just two days from being relieved of her duties by another submarine when at shortly after 1400hrs the lookouts on the coning tower spotted an object above the horizon to the south-west of their position. They quickly identified it as an airship and reasoned that it must be an allied aircraft given that by this point in the war German airships seldom ventured beyond the Western Front in France. The officer of the watch saw the airship turning towards them and having identified French roundels on the aircraft ordered that recognition rockets be readied to signal that they were a friendly vessel. A series of signal rockets were set up aft of the coning tower and the order was given for them to be fired. The brightly lit rockets shot upwards and in the wind arched over in the direction of the airship passing ahead of it as it droned forward towards the submarine.

In just a few seconds all hell broke loose on the deck of the submarine as bullets raked the hull from a machine gun mounted on the French airship. It was immediately obvious that the French had mistook the signal for an attack and were retaliating. Knowing the airship had bombs onboard Lieutenant Heriot-Maitland-Dougall gave the order to dive and the crew tried desperately to clamber inside their vessel as the airship droned closer, its machine gun still spewing bullets at the exposed crewmembers. As the submarine disappeared beneath the waves the airship was almost overhead and dropped two of its four light bombs which fell around 20m from the submarine.

The airship then made a second attack and dropped four bombs around the last known position of HMS D3. One by one the bombs exploded sending huge plumes of spray up in to the air before suddenly the coning tower broke the surface again. Heavily damaged from the French attack the crew made an effort to abandon their vessel but only four crewmembers made it off before the submarine disappeared below the surface for one last time.

The French airship cut its engines and began to descend in an effort to rescue the men and take them “prisoner”. Without the noise of their engines they heard the men speak as one of them shouted in English, “You’ve got us!” It was only then the French realised their mistake and made frantic efforts to organise a rescue for their Allies but it was all in vain. The French were unable to radio for assistance nor offer assistance themselves and by the time a vessel did reach the area the survivors had joined their comrades in the watery grave of HMS D3.

Naturally an investigation was launched and the commander of the French airship designated AT-0, Lieutenant Saint-Remy, was initially blamed by the British for the loss. However the investigation revealed that there was a certain degree of blame for both sides to accept. Attention was brought on the signal rockets fired by D3 which Saint-Remy took for an attack. It seems that the rockets were somehow rendered ineffective for the purposes of identification either because of atmospheric reasons such as haze or that the French crew, busy flying their airship, failed to properly identify them before they passed nearby leading them to the conclusion that they were under attack.

The investigation placed some blame on the British crew also. Signal rockets were common practice for the Royal Navy but the French Navy operated on the tactic of using smoke markers on the rear of their ships to identify them to Allied aircraft. The French argued that had the British crew done this instead of firing rockets then the attack would never have happened. But even they conceded that both sides should have been aware of their opposite number’s methods of identification. In the end Lieutenant Saint-Remy and his crew were exonerated of blame.

29 men died when HMS D3 sank in an example of what is now termed as friendly fire. The vessel has the somewhat sad distinction of being the only submarine to have been successfully engaged and sunk by a French aircraft in World War One.


11 responses to “HMS D3 – A Case of Mistaken Identity

  1. Pingback: Defence of the Realm – Royal Navy | Defence of the Realm

  2. A fascinating tale, and thank you for it. I can see why it was nobody’s fault, but why didn’t the donkeys in charge ever anticipate the results of a system that at best was ludicrous? Still I suppose these 29 men killed in the context of the casualties of the Great War is quite acceptable.

    Liked by 1 person

  3. Warfare is a fascinating subject. Despite the dubious morality of using violence to achieve personal or political aims. It remains that conflict has been used to do just that throughout recorded history.

    Your article is very well done, a good read.


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