The full statement would be: "In the presence of an active enemy, do not so divide your force that the enemy could attack each division in detail with a superior force." Napoleon was a past master in the art of overwhelming separate portions of an enemy's force, and he understood better than any one else of his time the value of concentration.

And yet a favorite plan of his was to detach a small part of his force, to hold a superior force of the enemy in check for--say a day--while he whipped another force of the enemy with his main body.

He then turned and chastised the part which had been held in check by the small detachment, and prevented from coming to the relief of the force that he attacked first.
When we say, then, that strategy directs how our naval force should be divided between the Atlantic and the Pacific, this does not mean that strategy should so divide it that both divisions would be confronted with forces larger than themselves.

It may mean, however, that strategy, in order that the force in one ocean shall be sufficient, may be compelled to reduce the force in the other ocean almost to zero.
Some may say that, unless we are sure that our force--say in the Atlantic--is superadequate, we ought to reduce the force in the Pacific to actual zero.

Maybe contingencies might arise for which such a division would be the wisest; but usually such a condition exists that one force is so large that the addition to it of certain small units would increase the force only microscopically; whereas those small units would be of material value elsewhere--say in protecting harbors from the raids of small cruisers.