The term cordon is used to denote every defensive plan which is intended directly to cover a whole district of country by a line of posts in connection with each other. We say directly, for several corps of a great army posted in line with each other might protect a large district of country from invasion without forming a cordon; but then this protection would not be direct, but through the effect of combinations and movements.
It is evident at a glance that such a long defensive line as that must be, which is to cover an extensive district of country directly, can only have a very small degree of defensive stamina. Even when very large bodies of troops occupy the lines this would be the case if they were attacked by corresponding masses. The object of a cordon can therefore only be to resist a weak blow, whether that the weakness proceeds from a feeble will or the smallness of the force employed.
With this view the wall of China was built: a protection against the inroads of Tartars. This is the intention of all lines and frontier defences of the European States bordering on Asia and Turkey. Applied in this way the cordon system is neither absurd nor does it appear unsuitable to its purpose. Certainly it is not sufficient to stop all inroads, but it will make them more difficult and therefore of less frequent occurrence, and this is a point of considerable importance where relations subsist with people like those of Asia, whose passions and habits have a perpetual tendency to war.
Next to this class of cordons come the lines, which, in the wars of modern times have been formed between European States, such as the French lines on the Rhine and in the Netherlands. These were originally