Page:Victory at Sea - William Sowden Sims and Burton J. Hendrick.djvu/101

1917] his enemy, or in giving him a good scare. If he always decided these two points accurately, he would almost always "get" his submarine ; the chances of error are very great, however, and that is the reason why the submarine in most cases gets away. All that the surface commander knows is that there is a U-boat somewhere in his neighbourhood, but he does not know its precise location and so he is fighting more or less in the dark. In the great majority of cases the submarine does get away, but now and then the depth charge reaches its goal and ends its career.

If only one destroyer is hunting, the chances of escape strongly favour the under-water craft ; if several pounce upon her at once, however, the chances of escaping are much more precarious. If the water is shallow the U-boat can sometimes outwit the pursuer by sinking to the bottom and lying there in silent security until its surface enemy tires of the chase. But in the open sea there is no possibility of concealing itself and so saving itself in this fashion, for if the submarine sinks beyond a certain depth the pressure of the water will crush it.

While the record shows that the U-boat usually succeeded in evading the depth charges, there were enough sunk or seriously damaged or given a bad shake-up to serve as a constant reminder to the crews that they ran great danger in approaching waters which were protected by destroyers. The U-boat captains, as will appear, avoided such waters regularly ; they much preferred to attack their merchant prey in areas where these soul-racking depth charges did not interfere with their operations.

It is now becoming apparent why the great battle fleet, which always sailed behind a protecting screen of such destroyers, was practically immune from torpedo attack. In order to assail these battleships the submarine was always compelled to do the one thing which, above all others, it was determined to avoid to get within depth-charge radius of the surface craft. In discharging the torpedo, distance, as already intimated, is the all-important consideration. The U-boat carries a torpedo which has a much shorter range than that of the destroyer; it was seldom effective if fired at more than 2,000 yards, and beyond that distance its chances of hitting became