The foregoing considerations are applicable to changes of position whether in the direction of the enemy, toward a flank, or to the rear. Flanking maneuvers and retrograde movements, both sometimes profitably employed to decoy the enemy, may frequently be utilized to gain advantageous relative position. The proper objective of each is the maintenance of a favorable situation, or the alteration of an unfavorable one, either locally or with reference to the larger phases of operations, through measures involving apportionment of fighting strength, or obtaining advantages of position, or retaining or gaining freedom of action. Combinations of forward, flanking, or retrograde movements are frequent in war, the skillful combination of the offensive and the defensive (see [page 75]) being no less applicable to the problem of relative position than to the other elements of a favorable military operation.
Procedure for Determination and Selection of Advantageous Relative Positions. Since the various positions to be occupied become physical objectives for the time being, their proper determination and selection are governed by the same considerations which apply to physical objectives (see [page 55] and following).
Thus, it becomes necessary to consider, first, as to suitability, whether the position, once gained, will permit the attainment of the appropriate effect desired.
Secondly, consideration is required as to feasibility. Are the available means adequate to gain or to maintain such position? In answering this question, due regard is paid to opposing means and to the characteristics of the theater.
Finally, there is to be considered, as to acceptability, whether the consequences as to costs, in terms of relative fighting strength, will be such, if the position is gained or maintained, as to permit the attainment of the objective. The possible effect of these consequences on future action, whether the attempt succeeds or fails, may be vitally significant.
With regard to suitability, the factor of the appropriate effect desired calls for special consideration of the requirements with a view to future action. This is true because of the relationship which naturally exists between successive positions ([page 60]) if changes of location from one to another are to be integrated into movement calculated to accomplish the effect desired. Each position, itself for the time being a physical objective, offers certain advantages or involves certain disadvantages with relation to a further physical objective. The position of the latter, in turn, presents possibilities (or denies them) with respect to future movement. The influence of considerations with respect to time (in addition to those noted above with regard to space) is also a factor whose importance increases when urgency is a matter of immediate concern.
With regard to feasibility, the technical capabilities and limitations of the armed forces ([page 67]) are, of course, among the principal factors. These capabilities and limitations are respectively promoted and imposed primarily by considerations peculiar to the particular medium of movement involved.
With specific regard to the areas within which military operations may suitably be undertaken, the fundamental distinctions created by recognized political sovereignty require attention. That part of the surface of the earth which comprises its land area is recognized as the property or the charge of one or another of the sovereign states, although in certain cases the title may be in dispute. The air above a nation's territorial domain is generally understood to be part of that domain. The point to be observed is that there are no land areas which belong equally to all nations. Accordingly; because of the factor of neutral sovereignty, both land and air forces of belligerent States may be under the necessity of following indirect routes to their physical objectives.
In the case of the sea, however, all those portions of the earth's surface which are covered by water (exclusive only of the recognized territorial waters of the several nations), i.e., the high seas, are presumably common property. The same applies to the air above the sea.