TO THE NEEDS OF THE UNITED STATES NAVY. 111 
Thus when submerged the submarine’s area of action resembles that of the tor- 
pedo which it carries as its chief weapon. It cannot chase to advantage when sub- 
merged. We cannot give a submarine the highest surface speed because of the 
heavily built hull and the heavy storage batteries. Such surface speed as we are 
able to confer on a submarine is inadequate for the tactical requirements of battle. 
It may enable a submarine to assume a favorable position for submerging ahead 
of an approaching enemy, but it cannot be great enough to be satisfactory in the 
tactical approach, as is the case with the torpedo-boat at 30 knots, which relies upon 
her great speed as a means of protection when charging upon the enemy. As the 
submarine when submerged cannot hope to overtake its target it must lie in wait 
for the target to come to it. 
Thus limited to moderate surface speed and low submerged speed, and unable 
to increase weights by the addition of armor, the submarine is obliged to rely upon 
her faculty for concealment as her chief means for employing her weapon, whether 
mine or torpedo. But concealment entails disadvantages. In hiding herself she be- 
comes blind, and if by the adoption of the periscope she has recovered partial sight, 
she has sacrificed a corresponding measure of invisibility. Before concealing her- 
self to attack, the submarine first must sight her enemy in order to direct her attack. 
To accomplish this to best advantage she must rise and search the horizon with 
natural vision. Unfortunately when so doing she cannot promptly submerge and 
is therefore liable to surprise attack. The submarine’s difficulty in seeing has con- 
sequences which extend beyond the individual ship. In warfare there is a com- 
batant advantage in superior numbers which is greater than the numerical ratio of 
the hostile forces (as may be mathematically shown). For this reason it has al- 
ways been reckoned a great point, both ashore and afloat, to bring superior forces to 
engage simultaneously upon the field of battle. But the submarine’s imperfect vi- 
sion occasions danger of interfering with friends when large submarine forces are 
concentrated for simultaneous concerted action, such as does not occur in the assem- 
blage of any type of surface craft. 
Thus the submarine is not only an arm to be used by stealth, but its most favor- 
able opportunities occur in dispersed and solitary action rather than in concentrated 
and co-ordinated action. 
Having thus glanced at the offensive and defensive capabilities of submarines 
we may now turn to the means of parrying their attack and of overcoming it. 
Until the outbreak of the current great war there seemed to be no adequate de- 
fense against submarine attack, but necessity is the mother of invention in tactics 
as well as in material, and there is less to fear from the submarine now than at the 
outbreak of the war. The great ships which the submarine would most gladly meet 
find their best protection is rapid motion; for the slow submarine, seeing imperfectly, 
is disconcerted by swift movement, more especially if this be accompanied by fre- 
quent alterations in direction. But ships cannot be always on the move, and it is nec- 
essary to provide both passive defense and active counter-attack against submarines. 
For harbors and certain sea areas the passive defense is furnished by wire nets 
