If the armies are very close in comparison to the width of their front, then it will often be impossible to post a vanguard between them, and the armies are obliged to place their dependence on a chain of outposts.
A concentrated corps, as it covers the approaches to the army less directly, generally requires more time and space to act efficiently; and therefore, if the army covers a great extent of front, as in cantonments, and a corps standing in mass is to cover all the avenues of approach, it is necessary that we should be at a considerable distance from the enemy; on this account winter quarters, for instance, are generally covered by a cordon of posts.
The second circumstance is the nature of the country; where, for example, any formidable obstacle of ground affords the means of forming a strong line of posts with but few troops, we should not neglect to take advantage of it.
Lastly, in winter quarters, the rigour of the season may also be a reason for breaking up