The year 1915 saw the gradual invention of a new kind of war activity which permanently transformed the actual image of the war. During 1915, the war cultures became enduringly crystallised around a body of mobilising themes, words and images which confirmed the meaning initially attributed to the war itself. The question of control of the seas was of central importance during the course of 1915. The blockade imposed on the Central Powers, and the submarine war designed in response to unlock its grip, were thus determining elements in totalisation of the conflict. The consequences of the blockade, in terms of food supply and the economy on the one hand and of military and diplomatic matters on the other, and, finally, of morale, were indeed considerable. They were to be an enduring burden throughout the rest of the war.