World War I saw a significant and tragic change to the prosecution of war. Allied passenger and merchant ships were blatantly attacked by the enemy, resulting in dreadful civilian losses. The mystery ships were then created - they were disguised as peaceful merchant ships, but which were equipped with guns hidden until a few seconds before opening fire on enemy submarines. They cruised on the trade routes, hoping to encounter enemy submarines and attract them to attack, and when the submarine came to the surface, bombard her with heavy armament. The guns had to be accurate, necessitating rigid drill and discipline - one officer or man making an error would give the show away and risk the ship and crew. This book, first published in 1928, is the first to tell the real story of life on board and the stories of attacks on and by submarines as well as describing the life on board - the discomforts, difficulties and dangers of this method of fighting back. There was also an explanation of the attraction this form of service has for men who were independent and courageous with a strict sense of moral duty. The crew were constantly on alert: one false step could lead to the ship being torpedoed, with those left to try and save themselves or being taken prisoner; discipline and readiness for immediate action were strict from the moment of leaving harbour until safe within the harbour on return. Campbell served on the mystery ships from 2015 to 2017, beginning as a Lieutenant-Commander R.N., and ending that part of his naval career as a Captain R.N. with a V.C. and three D.S.O.s. A little-known and over-looked part of war history. With illustrations by Lieutenant J.E. Broome, R.N.