getting near it. We might have learned that a German
U-boat was operating off Cape Cod; we might have had the
exact latitude and longitude of the location which it was
expected that it would reach at a particular moment. At
the time the message was sent the submarine might have
been lying on the surface ready to attack a passing merchantman, but even under these conditions the destroyer
could never have reached her quarry, for as soon as the
U-boat saw the enemy approaching it would simply have
ducked under the water and remained there in perfect
safety. When all danger had passed it would again have
bobbed up to the surface as serenely as you please, and gone
ahead with its appointed task of sinking merchant ships.
One of the astonishing things about this war was that many
of the naval officers of all countries did not seem to under-
stand until a very late date that it was utterly futile to send
anti-submarine surface craft out into the wide ocean to
attack or chase away submarines. The thing to do, of
course, was to make the submarines come to the anti-submarine craft and fight in order to get merchantmen.
I have made this point before, and I now repeat the explanation to emphasize that the patrol system was necessarily unsuccessful, because it made almost impossible any combats with submarines and afforded very little protection to shipping. The advantage of the convoy system, as its advocates now urged, was precisely that it made such combats inevitable. In other words, it meant offensive warfare. It was proposed to surround each convoy with a protecting screen of destroyers in precisely the same way that the battle fleet was protected. Thus we should compel any submarine which was planning to torpedo a convoyed ship to do so only in waters that were infested with destroyers. In order to get into position to discharge its missile the submarine would have to creep up close to the rim that marked the circle of these destroyers. Just as soon as the torpedo started on its course and the tell-tale wake appeared on the surface the protecting ships would immediately begin sowing the waters with their depth charges. Thus in the future the Germans would be compelled to fight for every ship which they should attempt to sink, instead of sinking them conveniently in waters that were free of destroyers, as had hitherto been their privilege. Already the British had demonstrated that such a screen of
