which had fixed and very limited duration, almost in accordance with the seasons, as either the feudal forces hastened home, or the pay for the condottieri used regularly to run short. Since large standing armies, with powerful trains of artillery mow down the opposition of walls or ramparts as it were with a machine, neither town nor other small corporation has any longer an inclination to hazard all their means only to be taken a few weeks or months later, and then to be treated so much the worse. Still less can it be the interest of an army to break itself up into garrisons for a number of strong places, which may for a time retard the progress of the enemy, but must in the end submit. We must always keep enough forces, over and above those in garrison, to make us equal to the enemy in the open field, unless we can depend on the arrival of an ally, who will relieve our strong places and set our army free. Consequently the number of fortresses has necessarily much diminished, and this has again led to the abandonment of the idea of directly protecting the population and property in towns by fortifications, and promoted the other idea of regarding the fortresses as an indirect protection to the country, which they secure by their strategic importance as knots which hold together the strategic web.
Such has been the course of ideas, not only in books but also in actual experience, at the same time, as usually happens, it has been much more spun out in books.
Natural as was this tendency of things, still these ideas were carried out to an extreme, and mere crotchets and fancies displaced the sound core of a natural and urgent want. We shall look into these simple and important wants when we enumerate the objects and conditions of fortresses all together; we shall thereby advance from the simple to the more complicated, and in the succeeding chapter we shall see what is to be deduced therefrom as to the determination of the position and number of fortresses.