favourable circumstances; the army can await the enemy behind the wood in a more or less concentrated position with a view to falling on him the moment he debouches from the road defiles. Such a forest resembles mountain in its effects more than a river: for it affords, it is true, only one very long and difficult defile, but it is in respect to the retreat rather advantageous than otherwise.
But a direct defence of forests, let them be ever so impracticable, is a very hazardous piece of work for even the thinnest chain of outposts; for abattis are only imaginary barriers, and no wood is so completely impassable that it cannot be penetrated in a hundred places by small detachments, and these, in their relation to a chain of defensive posts, may be likened to the first drops of water which ooze through a roof and are soon followed by a general rush of water.
Much more important is the influence of great forests of every kind in connection with the arming of a nation; they are undoubtedly the true element for such levies; if, therefore, the strategic plan of defence can be so arranged that the enemy’s communications pass through great forests, then, by that means, another mighty lever is brought into use in support of the work of defence.