In the North Sea, therefore, sea-power has exerted its greatest, most vital, and most far-reaching effect. There the Germans, if they had possessed the power, could have struck a blow which, if successful for them, would have proved a mortal stroke at the British Empire and would have rendered useless all the efforts of the Allies. Millions of men, incalculable volumes of guns, munitions, and stores of every imaginable kind for the use of the greatest armies ever set in the field, have entered the French ports solely because the Grand Fleet holds the guard in the North Sea. The whole face of the world would have been changed by German naval victory. England would have been subjected by invasion and famine. If the heart of the Empire had been struck, what would have been the future of its members? If sea communication with the Allies had been cut, what would have been their fate at the hands of the victors? The attacks of sallying cruisers and destroyers upon the coast towns of England, the “tip and run” raids, as they have been called, and the visits of bomb-dropping airships and aeroplanes are the signs of the naval impotence of Germany. The situation in the North Sea is, therefore, of absorbing interest. It may be studied chiefly from the two points of view of the strategy of the opposing fleets and the exercise of the blockade. There is a peculiarity in naval warfare, which is not found in warfare upon land, that a belligerent can withdraw his naval forces entirely from the theatre of war by retaining them, as with a threat, or in a position of weakness, behind the guns of his shore defences. Nothing of the kind is possible with land armies. A general can always find his enemy, and attack or invest him, and, if successful, drive him back, or cause him to surrender, and occupy the territory he has held. The Germans have chosen the reticent strategy of the sea. They have never come out to make a fight to a finish, to put the matter to the touch, “to gain or lose it all.” The _animus pugnandi_ is wanting to their fleet. It was necessary that they should do something. They could not lie for ever stagnant at Kiel and Wilhelmshaven. They could keep their officers and men in training by making brief cruises in and outside the Bight of Heligoland. They might, with luck, meet some portion of the Grand Fleet detached and at a disadvantage.