History of the World War

by Jr. Francis A. March; Richard J. Beamish

Inasmuch as the illegal use of the submarine by Germany brought America into the war it was extremely appropriate that she should take an active part in the suppression of the submarine menace. The methods which were used in fighting the submarines differed much in different cases. The action of the government in arming merchantmen and in providing them with trained gun crews did much to lower the number of such ships sunk by the U-boats.

The submarine, which had formerly been able to stop the unarmed merchantman and sink him at leisure, after a few combats with an armed merchantman began to be very wary and to depend almost entirely upon his torpedoes. It was not always easy for the submarine to get in a position where her torpedo would be effective, and the merchantman was carefully directed, if attacked, to pursue a ziz-zag irregular course, and at the same time endeavor to hamper the submarine by shooting as near her periscope as possible.

Along the sea coasts and at certain points in the English Channel great nets were used effectively. Submarines, however, toward the end of the war were made sufficiently large to be able to force their way through these nets, and net-cutting devices were also used by them with considerable effect. The best way to destroy the submarines seemed to be in a direct attack by flotillas of destroyers.

By the end of the war the whole process of sinking or destroying submarines had been thoroughly organized. Practically every portion of the seas near Great Britain and France was carefully watched and the appearance of a submarine immediately reported. As the submarine would only travel at a certain well-understood speed during a given time, it was possible to calculate, after the locality of one was known, about how far from that point it would be found at any later period. Destroyers were therefore sent circling around the point where the submarine had been discovered, enlarging their distance from the center every hour. In the course of time the submarine would be compelled to come up for air, and then, if luck were with the destroyer, it might find its foe before it was seen itself. Having discovered the submarine the destroyer immediately endeavored to ram, dropping depth bombs at the point where they supposed the enemy to be.

These bombs were so constructed that at a certain depth in the water they would explode, and the force of the explosion was so great that even if they did not strike the submarine they would be sure to damage it seriously, sometimes throwing the submarine to the surface partly out of water, and at other times driving her to come to the surface herself ready to surrender.

In many cases it was not necessary to use the depth bomb at all. The gunners on board the destroyers had become extraordinarily expert, and though a shot might destroy the periscope of a submarine without doing much damage, most submarines carrying extra periscopes to use if necessary, yet it was soon found that it was possible by the use of plunging shells to do effective damage. Plunging shells are somewhat similar in their operation to bombs. Such a shell falling just short of a periscope and fused to burst both on contact and at a certain depth was extremely likely to do damage.

In the pursuit of the U-boat the airplane was also extremely effective. These were sent out to patrol large districts near the Allied coast, and also, in some cases, from ships themselves. It is possible in certain weather conditions for the observer on an airplane to detect a submarine even when it is submerged and the airplane can not only attack the submarine by dropping depth bombs, but it can signal at once the location of the enemy to the hurrying destroyers. Indeed, as the submarine warfare proceeded the main difficulty of the Allies was to locate the submarines. Many ingenious devices were used for this purpose, and many of the English vessels had listening attachments under water which were intended to make it possible to hear a submarine as it moved. These, however, do not seem to have been very effective. The submarine itself seems at times to have been fitted out in a similar way and to have thus been able to hear the sound of an approaching ship.

Many thrilling reports of naval actions against German submarines were given out officially by the British admiralty from time to time. In most of these cases the submarine was both rammed and attacked by depth bombs. In nearly all of them the only proof of success was the oil and air bubbles which came to the surface.

One interesting encounter was that in which a British submarine sighted a German U-boat, while both were on the surface. The British submarine dived and later was able to pick up the enemy through the periscope and discharge a torpedo in such a way as to destroy the German vessel. When the British submarine arose it found a patch of oil in which Germans were swimming.

Ordinarily, however, a submarine was of little service in a fight against another for the radius of sight from a periscope is so short that it is practically blind so far as another periscope is concerned. This blindness of the submarine was taken advantage of by the Allies in every possible way.