The Art of War by active 6th century B.C. Sunzi

21. The natural formation of the country is the soldier’s best ally;

[Ch’en Hao says: "The advantages of weather and season are not equal to those connected with ground."] but a power of estimating the adversary, of controlling the forces of victory, and of shrewdly calculating difficulties, dangers and distances, constitutes the test of a great general.