The second great difference lies in the totally different problems which movement creates in battle. In battle practice the only movement of the target is that which the towing ship can give to it. Its speed and manœuvring power are strictly limited, whereas a 30-knot battle-cruiser can change speed and direction at will. The smallest change of course must alter the range, and the smallest miscalculation of speed or course must make accurate forecast of range impossible. But the movements of the target are only a part of the difficulty. Those that arise from the manœuvres of the firing ship may be still greater and more confusing. And so obvious is this that, in peace time, it used to be almost an axiom that to put on helm during an engagement--even for the sake of keeping station--should be regarded almost as a crime. But the long-range torpedo has long since made it clear that a firing squadron may _have_ to put on helm. It must manœuvre, that is to say, in self-defence--a thing it would never have to do in battle practice. And when both target ship and firing ship are manœuvring, it is small wonder if methods of fire control, designed primarily for steady courses by one ship and low speed and small turns by the other, break down altogether. It is undoubtedly true that the mainspring of all defensive naval ideas is _doubt as to the success of offensive action_, and as the only offensive action that a battleship can take is by its guns, it would seem as if those who disbelieve in the offensive have had far too much reason for their scepticism. THE TORPEDO IN BATTLE It was the invention of the hot-air engine round about 1907 that converted the torpedo from a short- to a long-range weapon, and when, a year or two later, the feasibility of running one of these with almost perfect accuracy and regularity to a distance of five miles was demonstrated, it became quite obvious that a new and, as many thought, a decisive element had been introduced into naval war, the effect of which would be especially marked in any future fleet actions. Just what form its intervention would take was much discussed in three years, and the following quotation from a confidential contribution of my own on this discussion, written in December 1912, is perhaps not without interest as indicating the points then in debate: “The tactical employment of fleets has, of course, recently been complicated, in the opinions of many, by the facts that the range of torpedoes is more than doubled; that their speed is very greatly increased; and that their efficiency (that is, the extent to which they can be relied upon to run well) has increased almost as much as their range and speed. This advance of the torpedo has followed very rapidly on the development of the submarine, and has led, quite naturally, to the suggestion that it should be employed on a considerable scale in a fleet action either from under-water craft or by squadrons of fast destroyers.