“When the first submarine torpedo-boat goes into action she will bring us face to face with the most puzzling problem ever met in warfare. She will present the unique spectacle, when used in attack, of a weapon against which there is no defence. You can pit sword against sword, rifle against rifle, cannon against cannon, ironclad against ironclad; you can send torpedo-boat destroyers against torpedo-boats, and destroyers against destroyers, but you can send nothing against the submarine boat, not even itself. You cannot fight submarines with submarines. The fanciful descriptions of the submarine battle of the future have one fatal defect. You cannot see under water. Hence you cannot fight under water. Hence you cannot defend yourself against an attack under water except by running away. If you cannot run away you are doomed. Wharves, shipping at anchor, the buildings in seaport towns, cannot run away, therefore the sending of a submarine against them means their inevitable destruction. No; as nearly as the human mind can discern now, the submarine is indeed a ‘sea-devil’ against which no means that we possess at present can prevail. It is no use for the defence to mine, for the submarine would countermine, and torpedo nets would be of no use, for it would blow a hole through them, and any attempt to discover the position of the boat when below the surface is about as promising a pursuit as dredging with a butterfly-net for a half-dollar that had been thrown into New York Bay.” In the present state of the science of submarine warfare it is certainly impossible to fight submarines with submarines, and it is recognised that the best chance of destroying an under-water vessel is when it comes to the surface to take a momentary glance at the position of its victim before launching its torpedo. When a means of distinguishing objects beneath the waves has been evolved then it will be time enough to discuss the possibility of constructing a submarine boat destroyer which shall itself go beneath the surface and seek out the submarine to deal it its deathblow. Every advance in military and naval science that tends to strengthen the attack has been met by some invention or device calculated to enable the defence to withstand it. In the early days men went into battle wearing heavy armour, but nowadays, although bullet-proof cuirasses and bullet-proof shields have been suggested, the foot soldier carries no protection on his person, but relies instead upon entrenchments and fortifications.