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.

The easiest and quickest path into the esteem of traditional military authorities is by the appeal to the eye, rather than to the mind. The `polish and pipeclay' school is not yet extinct, and it is easier for the mediocre intelligence to become an authority on buttons, than on tactics.

The theory of the indirect approach operates on the line of least expectation.

Natural hazards, however formidable, are inherently less dangerous and less uncertain than fighting hazards. All conditions are more calculable, all obstacles more surmountable than those of human resistance.

Air Power is, above all, a psychological weapon - and only short-sighted soldiers, too battle-minded, underrate the importance of psychological factors in war.

In war the chief incalculable is the human will, which manifests itself in resistance, which in turn lies in the province of tactics. Strategy has not to overcome resistance, except from nature. Its purpose is to diminish the possibility of resistance, and it seeks to fulfil this purpose by exploiting the elements of movement and surprise.

No man can exactly calculate the capacity of human genius and stupidity, nor the incapacity of will.