It is the connection which exists between War and country or ground.
This connection is, in the first place, a permanent condition of War, for it is impossible to imagine our organised Armies effecting any operation otherwise than in some given space; it is, secondly, of the most decisive importance, because it modifies, at times completely alters, the action of all forces; thirdly, while on the one hand it often concerns the most minute features of locality, on the other it may apply to immense tracts of country.
In this manner a great peculiarity is given to the effect of this connection of War with country and ground.

If we think of other occupations of man which have a relation to these objects, on horticulture, agriculture, on building houses and hydraulic works, on mining, on the chase, and forestry, they are all confined within very limited spaces which may be soon explored with sufficient exactness.
But the Commander in War must commit the business he has in hand to a corresponding space which his eye cannot survey, which the keenest zeal cannot always explore, and with which, owing to the constant changes taking place, he can also seldom become properly acquainted.

Certainly the enemy generally is in the same situation; still, in the first place, the difficulty, although common to both, is not the less a difficulty, and he who by talent and practice overcomes it will have a great advantage on his side; secondly, this equality of the difficulty on both sides is merely an abstract supposition which is rarely realised in the particular case, as one of the two opponents (the defensive) usually knows much more of the locality than his adversary.
This very peculiar difficulty must be overcome by a natural mental gift of a special kind which is known by the--too restricted--term of Orisinn sense of locality.

It is the power of quickly forming a correct geometrical idea of any portion of country, and consequently of being able to find one's place in it exactly at any time.

This is plainly an act of the imagination.