Particularly must one beware of permitting the enemy to retain advantages in topography; always and at once he should be dislodged from posts whose continued occupation may facilitate his giving an unforeseen and often a fatal blow. The full importance of topography perhaps is best expressed in the following dictum by the great Frederic: PRINCIPLE “_Whenever a general and decisive topographical advantage is presented, one has merely to avail of this, without troubling about anything further._” The relative advantage in Topography possessed by one army over an opposing army, always can be determined by the following, viz.: RULE 1. If the principal adverse Corps of Position are situated upon points of a given color, and if the principal Kindred Corps of Position are situated upon points _not_ of the given color, then: That army which has the _more_ Corps of Evolution able to act against points of the given color, and the _equality_ in Corps of Evolution able to act against points of the opposite color, has the relative advantage in Topography. 2. To utilize the relative advantage in Topography, construct a position in which the kindred Corps of Position necessary to be defended shall occupy a point upon the sub-geometric symbol of a kindred Corps of Evolution; which point shall be a Tactical Key of a True Strategetic Horizon of which the kindred Corps of Evolution is the Corps of the Centre and of which either the adverse King or an undefendable adverse piece is the second Tactical Key. 3. To neutralize the relative disadvantage in Topography, eliminate that adverse Corps d’armee which is able to act simultaneously by its geometric symbol against the principal Kindred Corps of Position upon a given color; and by its sub-geometric symbol against points of opposite color. * * * * * Perfection in Defensive Topography is attained whenever the ground occupied nullifies hostile advantages in Time, Organization, Mobility, Numbers and Position. Perfection in Offensive Topography is attained whenever the ground occupied accentuates the kindred advantages in Time, Organization, Mobility, Numbers and Position. MILITARY EXAMPLES _“When you intend to engage in battle endeavor that your CHIEF advantage shall arise from the ground occupied by your army.”--Vegetius._ To cross the Granicus, Alexander the Great selected a fordable spot where the river made a long, narrow bend, and attacked the salient and both sides simultaneously. The Persians thus outflanked were easily and quickly routed; whereupon the Grecian army in line of Phalanxes, both flanks covered by the river and its retreat assured by the fords in rear, advanced to battle in harmony with all requirements of Strategetic Art. * * * * *