Napoleon's Maxims of War
https://www.gutenberg.org/files/50750/50750-h/50750-h.htm#NAPOLEONS
Excerpts dealing with strength and fortifications.
Maxim X: "When an army is inferior in number, inferior in cavalry, and in artillery, it is essential to avoid a general action. The first deficiency should be supplied by rapidity of movement; the want of artillery, by the nature of the manœuvres; and the inferiority in cavalry, by the choice of positions. In such circumstances, the
morale of the soldier does much."
Maxim XIV: "Among mountains, a great number of positions are always to be found very strong in themselves, and which it is dangerous to attack. The character of this mode of warfare consists in occupying camps on the flanks or in the rear of the enemy, leaving him only the alternative of abandoning his position without fighting, to take up another in the rear, or to descend from it in order to attack you. In mountain warfare, the assailant has always the disadvantage; even in offensive warfare in the open field, the great secret consists in defensive combats, and in obliging the enemy to attack."
Maxim XVII: "In a war of march and manœuvre, if you would avoid a battle with a superior army, it is necessary to entrench every night, and occupy a good defensive position. Those natural positions which are ordinarily met with, are not sufficient to protect an army against superior numbers without recourse to art."
Maxim XLI: "If the besieging force is of numerical strength enough (after leaving a corps before the place four times the amount of the garrison) to cope with the relieving army, it may remove more than one day’s march from the place; but if it be inferior in numbers after providing for the siege, as above stated, it should remain only a short day’s march from the spot, in order to fall back upon its lines, if necessary, or receive succor in case of attack.
If the investing corps and army of observation are only equal when united to the relieving force, the besieging army should remain entire within, or near its lines, and push the works and the siege with the greatest activity."
Maxim XLIII: "Those who proscribe lines of circumvallation, and all the assistance which the science of the engineer can afford, deprive themselves gratuitously of an auxiliary which is never injurious, almost always useful, and often indispensable. It must be admitted, at the same time, that the principles of field-fortification require improvement. This important branch of the art of war has made no progress since the time of the ancients. It is even inferior at this day to what it was two thousand years ago. Engineer officers should be encouraged in bringing this branch of their art to perfection, and in placing it upon a level with the rest."