Underwater craft, however, are very vulnerable. Damage which would be trifling to a surface ship may prove fatal to a vessel which has to rely upon rer power of submergence. Moreover, since submarines can be forced to dive by fast surface ships and aircraft, in which condition they are slow and virtually blind, their command of the sea they Occupy is necessarily precarious.
During a protracted war not more than about one-third of a country's submarine fleet can be expected to be at sea at any particular time. The remainder must he in harbour, refitting and resting their crews. And to this the highly specialized training necessary, the moral effect of the inevitable losses and disappearances, and the constant strain upon the personnel through the greatly enhanced methods of location and destruction, and it is obvious that the successful operation of submarines has become increasingly difficult and dangerous.
However ably handled, they can never be a match for surface warships suitably protected by destroyers and aircraft." Given an adequate convoy system, with escort vessels,-hunting flotillas and aircraft, they should be far less of a menace to merchantmen than during the last year of the Great War, when, with a convoy stem in force and anti-submarine operations in full swing, no fewer than sixty-nine U-boats were sent to the bottom by one means or another.
Text read from the printed page and cleaned; old type leaves the occasional error.