Where armies have not been so dependent, strategy has been correspondingly handicapped, and the tactical issue of battle has played a greater part. Nevertheless, even thus handicapped, strategic artists have frequently gained a decisive advantage previous to battle by menacing the enemy's line of retreat, the equilibrium of his dispositions, or his local supplies.
To be effective such a menace must usually be applied at a point closer, in time and space, to the enemy's army than a menace to his communications, and thus in early warfare it is often diffi cult to distinguish between strategical and tactical manoeuvre.
In the psychological sphere, dislocation is the result of the im pression on the commander's mind of the physical effects which we have listed. The impression is strongly accentuated if his realization of being at a disadvantage is sudden, and if he feels that he is unable to counter the enemy's move. Psychological dislocation, indeed, fundamentally springs from the sense of being trapped. This is the reason why it has most frequently followed a physical move onto the enemy's rear. An army like a man can not properly defend its back from a blow without turning round to use its arms in the new direction. "Turning" tempo rarily unbalances an army as it does a man, and with the former the period of instability is inevitably much longer. In conse quence, the brain is much more sensitive to any menace to its back. In contrast, to move directly on an opponent is to consoli date his equilibrium, physical and psychological, and by consoli dating it to augment his resisting power. In war as in wrestling the attempt to throw the opponent without loosening his foothold and balance tends to self-exhaustion, increasing in disproportion ate ratio to the effective strain imposed upon him. Because of this disproportion, which increases as the effort advances, victory by such a method can only be attainable if the assailant possesses a great margin of strength. Even so, it tends to lose decisiveness, for in the case of an army it rolls the enemy back towards their reserves, supplies and reinforcements, so that as the original front is worn thin new layers are added to the back. And, at best, it imposes a strain rather than producing a jar.
Thus a move round the enemy's front against his rear has the aim not only of avoiding resistance on its way but in its issue.
In the profoundest sense, it takes the line of least resistance. The equivalent in the psychological sphere is the line of least expecta tion. They are the two faces of the same coin, and to appreciate this is to widen our understanding of strategy. For if we merely take what obviously appears the line of least resistance, its obvi ousness will appeal to the opponent also and this line may no longer be that of least resistance. In studying the physical aspect we must never lose sight of the psychological, and only when both are combined is the strategy truly an indirect approach, calculated to dislocate the opponent's equilibrium.
Examples.—Hannibal in 217 B.C. took the line of least resis tance and least expectation by moving into Etruria through the marshes and on to the rear of the Roman army encamped at Arretium. But, after ravaging the country, he then moved straight on, and by thus appearing to ignore contemptuously this Roman army impelled the consul Flaminius far more strongly than by any threat to his rear or supplies to rush precipitately on Hanni bal's heels and into the deadly ambush at Lake Trasimene (q.v.).
Schlieffen, framing the German plan for 1914, sought a logistical indirect approach by sweeping through Belgium with a massive right wing. But the real subtlety of his plan was not on his right but on his left, which he made so weak that any French offensive in Lorraine would push it back. And the further it was pushed back, the further would the French be committed in this direction and the more would their rear be exposed to the sweep of his right wing through Belgium. Like a neck their communications would be stretched out to receive the falling axe. The plan was shrewdly based on an insight into the French temperament and their new doctrine of the headlong offensive. Indeed, in the event the French "head" was laid blindfold on the block. But unfortunately for Germany, Schlieffen's successor, Moltke, failed to grasp his con ception and, fearing the weakness of the left wing, so strengthened this as to counteract its essential purpose. While the French rushed to fall into the trap, Moltke rushed German troops to save them. An irony of history.