The following is written of a combination of two or more true war incidents. It is intended to illustrate what the writer considers to be the true strategic use of patrol submarines.
After 1916 the Submarine Patrol flotillas that watched the exit of the Heligoland Bight were given certain orders, which altered altogether their duties and their _raison d'être_. These were to the effect that no outward-bound ship of the enemy was to be attacked or fired at until a signal had first been made by the sighting submarine, to report such enemy's presence and movement; only homeward-bound ships could be fired at, and if outward-bound ships were seen, the reporting signal was to be made at all costs. This alteration detracted somewhat from the interest of submarine war, but it added largely to the strategic usefulness of our patrol boats. It is of no use to torpedo an enemy ship and thereby lose a chance for the Grand Fleet of cutting off the whole enemy force, and a torpedo fired meant that an hour or more of depth-charging would follow the shot, and prevent the signal being made before the news of the enemy's position had grown cold.
The submarine was a J boat, and her station was at the western end of the North Dogger Bank-Heligoland swept channel. The weather had been rough and wet for the first four days of her patrol, reducing the periscope visibility to a few hundred yards' range across grey and foaming seas. The boat had patrolled at twenty feet depth (which is shallow for a big boat) in order to see anything at all, and because of the steep seas she had kept always beam to them, except for the turns at the end of her ten-mile beat. Each turn had caused her to either break surface or slip down to eighty feet, owing to the quick inclinations given her as the waves met her end-on. The weather cleared suddenly on the fourth night, and next morning she dived at dawn, under a gentle swell that hourly died down to a calm deep blue ocean. The visibility was good--how good her captain had hardly realised until through his high-power periscope he picked up the unmistakable line of brown blurs to the east that meant an approaching enemy squadron at a range of at least ten miles. He turned and dived at half-speed towards them, calling his crew to "action stations" at once. He knew that his orders forbade him to fire, but there was always the chance of his having to use his torpedoes in self-defence--self-defence, that is, of a legitimate kind, not of the type said to be used in certain districts where only mad elephants are allowed to be killed, but where all the elephants are said to became indubitably mad "after the first shot." As the smoke-blurs grew he eased speed to "dead slow"; the enemy was shown by the rate of change of his bearings to be steering a course which would take him past the J boat at easy range. The periscope slid along very slowly, only about a foot of its length showing above water; the captain knew that he could see Zeppelins if they were about, but an aeroplane, especially against the sun, is a different proposition, and he did not want to risk being observed before his wireless had done its work. Twenty minutes from sighting the smoke he turned to east to pass parallel to the enemy, and he moved slowly past their line. Looking closely at them with the high-power instrument, and with his periscope top now a bold three feet above the surface, he spoke rapidly and briefly to his third officer, who, notebook in hand, stood at his elbow--