2. The first condition governing the dimensions of oversea attack from Germany is the number of troops available—
(i.) Instantly;
(ii.) In twenty-four hours; and
(iii.) At any time after a general mobilisation is complete.
5. A second great limiting condition is the shipping available in German ports. For all phases after the war has become open, whether under 1, 2, or 3, ample shipping is available of every class required, and the matter need not be further considered. But in case 1, the invading force is limited by the amount of suitable shipping available instantly at the right ports, and secondly, by what is available after 24 hours: in case 2 by the amount of shipping available instantly. After that, when war has actually begun, there is no difficulty in finding the ships or the men; the only difficulty is to get them across.
6. The third condition is the time taken to embark, transport, and land the various forces at different points concurrently and alternatively. This requires separate calculations in every case. These are complicated by the hours of daylight and darkness, the tides, the weather, and other uncertain features. Each case must be worked out separately, and risked on its merits.
7. The last consideration is the distance of the practicable objective from the landing-point. Here again each case must be considered individually:—
Harwich is invaluable because it threatens London, and is unquestionably the best place for so doing. In no other way could you react so instantaneously upon British public opinion. On the other hand, once the invaders were turned out, the actual damage done would be small.
Immingham is a purely local injury not worth touching before war breaks out, and afterwards belonging to the ‘driblets’ phase.