The reasons which make it necessary to be more cautious when dealing with the attack of under-water weapons than with gun attack are the greater damage which one torpedo hit will cause, which damage may well be fatal to many ships, in most cases compelling the ship to reduce speed and leave the line of battle. With the gun, it is usually different; a ship which is being heavily hit can—if her own offensive powers will not save her by crushing the fire of the enemy—so manœuvre as to derange temporarily the accuracy of that fire. Therein lies the whole necessity for the exercise of care when dealing with the underwater weapon.
These considerations led me to introduce measures for dealing with destroyer attacks on the Battle Fleet other than the counter of attack by our light craft on the enemy’s destroyers. These measures involved a turn on the part of the ships, either towards the torpedoes or away from them.
In the first case, the object was to turn the ships so that they would present as small a target as possible to the torpedo, and incidentally that the space between the ships should be correspondingly large. The matter is very technical, and presents many interesting features, one of which may be illustrated by an example:
Generally speaking a safe course to pursue is for ships to steer direct for the attacking destroyers if the moment at which the torpedoes are fired can be ascertained.
This course, although applicable to one attack, leads to difficulties in the case of successive attacks, since further turns towards will bring the battle line within effective range of torpedoes fired from the enemy’s battleships; occasions will arise when this risk must be accepted.
The accompanying diagram shows that the van and centre squadrons are not so well safeguarded by a turn towards the attacking destroyers as is the rear squadron, for if the enemy’s flotilla is seen to fire torpedoes from C (a threatening position to the van) and the van squadron turns inwards 4 points, the 4th ship of the squadron will steer along the line A B.
If the torpedoes have been fired at the rear squadron instead of the van squadron as supposed, and their objective is the twentieth ship in the line, they will run along the line C D, i.e., directly at the fourth ship in the line.
The target presented is, however, small, and the chances of a flotilla attacking the rear squadron when in a favourable position for attacking the van are not great.
The important point in the case of a turn towards is, however, the necessity for ascertaining the moment of discharge of the torpedoes.