For if we merely take what obviously appears the line of least resistance, its obviousness 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 balance.
B. H. Liddell HartTo ensure attaining an objective, one should have alternate objectives. An attack that converges on one point should threaten, and be able to diverge against another. Only by this flexibility of aim can strategy be attuned to the uncertainty of war.
B. H. Liddell HartThe more closely [the German army] converged on [Stalingrad], the narrower became their scope for tactical manoeuvre as a lever in loosening resistance. By contrast, the narrowing of the frontage made it easier for the defender to switch his local reserves to any threatened point on the defensive arc.
B. H. Liddell HartWith growing experience, all skillful commanders sought to profit by the power of the defensive, even when on the offensive.
B. H. Liddell Hart