Named after the Isle of May, a nearby island in the Firth of Forth, the "battle" consisted of a disastrous series of accidents amongst Royal Navy vessels on their way from Rosyth, Scotland, to fleet exercises in the North Sea.

On the afternoon of 31 January 1918, around forty naval vessels left Rosyth on the Firth of Forth, Scotland, bound for Scapa Flow in Orkney where exercises involving the entire Grand Fleet would take place the following day.

The K-class submarines, specially designed to operate with a battle fleet, were large boats for their time, at 339 feet (103 m) long.

[3] Vice Admiral Beatty had moved the 12th and 13th flotillas of K-class submarines in December 1917 from Scapa Flow to Rosyth in order to ensure that they were in a better strategic location from which to undertake operations.

At 18:30 hours the vessels weighed anchor, and the entire fleet under the command of Vice Admiral Sir Hugh Evan-Thomas in the battlecruiser HMS Courageous steamed in a single line nearly 30 miles (48 km) long.

To avoid attracting German U-boats, particularly as one was suspected to be in the area, after dark each vessel showed only a dim blue stern light accompanied by black-out shields that restricted the lights to one compass point either side of the boats' centre line, and they also were all instructed to maintain radio silence.

At approximately 19:00 hours, Courageous passed the Isle of May and increased speed, just as a low-lying bank of mist settled over the sea.

Both stricken submarines stopped and carefully pulled themselves apart whilst the rest of the flotilla, unaware of what had happened, continued out to sea.

[citation needed] This could have made a difference and prevented the loss of at least some of those in the water, except that the primitive technology of the time meant that transmission was delayed until 21:20.

K3 narrowly missed K4 and then stopped three cables further on, but K6, despite going full astern, could not avoid a collision, ramming the broadside of K4 and nearly cutting the latter in half.

The Court of Inquiry released its final report on 19 February 1918, in which it placed the blame for the incident on Leir and four officers on the K boats.

[1] In 2011, surveyors conducting a detailed preparatory survey of the sea floor for the Neart Na Gaoithe offshore wind farm published sonar images of the wrecks of the two submarines, K-4 and K-17, sunk during the accident.