Operation E.C.1, usually called by the sardonic name of the Battle of May Island, or sometimes the geographically correct Battle of the Isle of May, was a disastrous series of accidents amongst Royal Navy ships on their way from Rosyth in Scotland to fleet exercises on the misty night of 31 January to 1 February 1918. This saw the loss of two submarines, damage to three other submarines and a light cruiser, and the deaths of over 100 men, all of the Royal Navy. Although it took place during the First World War it was an entirely accidental tragedy and no enemy forces were present.