At 18:30 hours on 31st January 1918 a group of Royal Navy ships set sail from Rosyth. They were headed to Scapa Flow where they were to take part in a fleet exercise. There were some 40 ships and boats in the group, including three battleships and four battlecruisers, each with their destroyer screens, and two flotillas of K-class submarines.
The 12th flotilla comprised K3, K4, K6 and K7 and was led by HMS Fearless, a light cruiser; the 13th flotilla comprised K11, K12, K14, K17 and K22, led by HMS Ithuriel, a destroyer.
The K-class submarines were unusual in that other submarines were designed to operate independently; K-class submarines were meant to take part in fleet actions. They were driven by steam turbines and could travel at up to 24 knots, keeping station with the rest of the fleet. They would submerge only when the enemy fleet was sighted and take part in the battle which followed.
Unfortunately there were design flaws that made them rather dangerous. They could take up to 30 minutes to submerge; in bad weather when operating on the surface, water could find its way down the funnels and extinguish the boiler fires; they were 103m long and had an estimated maximum safe depth of 61m. This meant that even in a shallow dive the bow could reach maximum depth when the stern was still on the surface.
The sailors who served on these boats were well aware of these problems; they referred to them as “Kalamity” class or even “Killer” class.
On the evening in question, there was a mist; all the vessels taking part were steaming in line astern, some 400 yards apart with only a single blue light showing at the stern.
At about 19:00 as the 13th flotilla neared May Island at the mouth of the Forth estuary, lights were seen approaching the submarines. These lights have never been positively identified, but were probably minesweeping trawlers. The submarines were forced to take evasive action, and K-22 lost sight of the other submarines in the mist and collided with K-14, causing the deaths of two sailors.
K-22 broke radio silence to report the incident and fired flares, causing the rapidly approaching battlecruisers to avoid the damaged submarines but HMS Inflexible struck K-22 a glancing blow which caused severe damage.
By now, HMS Ithuriel had learned of the collision and incredibly turned back to render assistance after sending a coded message to HMAS Australia. The 13th flotilla followed HMS Ithuriel and also turned back. The two submarine flotillas were now on collision course.
HMS Fearless, leading the 12th flotilla, collided at speed with K-17, causing her to sink in just a few minutes and killing 48 members of her crew. HMS Fearless was brought to a halt but the submarines following her had to take evasive action. Unfortunately K-6 was unable to avoid K-4 and rammed her, causing such severe damage that K-4 was almost cut in two and sank rapidly with all hands.
In just over an hour, two submarines had been sunk, three submarines and a cruiser had been damaged and 104 sailors had lost their lives.
There was of course an investigation, which was held in February 1918; this was followed by the Court Martial of the captain of HMS Ithuriel, Commander Leir. The case against him was not proved and the whole affair was hushed up. The relatives of those who died were told only that their kinfolk had lost their lives on active service. The full details of the incident were not released until 1994, after the death of the last survivor.
A memorial cairn was erected in June 2002 at Anstruther harbour in Fife and a Memorial service was held on 31st January 2018, attended by members of Queensferry History Group.
Sonar scans of the two wrecked submarines can be found online and clearly show the fatal damage to both boats.
Richard Squires 2022
Queensferry History 
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