not continue to employ so large a detachment, he must convert the investment into a siege, and take the place. From the moment the siege commences, it is then chiefly the passive efficacy of the fortress which comes into action.
All the destinations of fortresses which we have been hitherto considering are fulfilled in a simple and mainly in a direct manner. On the other hand, in the next two objects the method of action is more complicated.
- As a protection to extended cantonments. That a moderate-sized fortress closes the approach to cantonments lying behind it for a width of three or four milesis a simple result of its existence; but how such a place comes to have the honour of covering a line of cantonments fifteen or twenty miles in length, which we find frequently spoken of in military history as a fact—that requires investigation as far as it has really taken place, and refutation so far as it may be mere illusion.
The following points offer themselves for consideration:—
(1.) That the place in itself blocks one of the main roads, and really covers a breadth of three or four miles of country.
(2.) That it may be regarded as an exceptionally strong advanced post, or that it affords a more complete observation of the country, to which may be added facilities in the way of secret information through the ordinary relations of civil life which exist between a great town and the adjacent districts It is natural that in a place of six, eight or ten thousand inhabitants, one should be able to learn more of what is going on in the neighbourhood than in a mere village, the quarters of an ordinary outpost.
(3.) That smaller corps are appuyed on it, derive from it protection and security, and from time to time can advance towards the enemy, it may be