He grasped only the head and not the feet of Foch’s principles

From the Guns of August by Barbara Tuchman.

Though a profound student of Clausewitz, Foch did not, like Clausewitz’s German successors, believe in a foolproof schedule of battle worked out in advance. Rather he taught the necessity of perpetual adaptability and improvisation to fit circumstances. “Regulations,” he would say, “are all very well for drill but in the hour of danger they are no more use … You have to learn to think.” To think meant to give room for freedom of initiative, for the imponderable to win over the material, for will to demonstrate its power over circumstance.

But the idea that morale alone could conquer, Foch warned, was an “infantile notion.” From his flights of metaphysics he would descend at once, in his lectures and his prewar books Les Principes de la Guerre and La Conduite de la Guerre, to the earth of tactics, the placing of advance guards, the necessity of sureté, or protection, the elements of firepower, the need for obedience and discipline. The realistic half of his teaching was summed up in another aphorism he made familiar during the war, “De quoi s’agit-il?” (What is the essence of the problem?)

Eloquent as he was on tactics, it was Foch’s mystique of will that captured the minds of his followers. Once in 1908 when Clemenceau was considering Foch, then a professor, for the post of Director of the War College, a private agent whom he sent to listen to the lectures reported back in bewilderment, “This officer teaches metaphysics so abstruse as to make idiots of his pupils.” Although Clemenceau appointed Foch in spite of it, there was, in one sense, truth in the report. Foch’s principles, not because they were too abstruse but because they were too attractive, laid a trap for France. They were taken up with particular enthusiasm by Colonel Grandmaison, “an ardent and brilliant officer” who was Director of the Troisième Bureau, or Bureau of Military Operations, and who in 1911 delivered two lectures at the War College which had a crystallizing effect.

Colonel Grandmaison grasped only the head and not the feet of Foch’s principles. Expounding their élan without their sureté, he expressed a military philosophy that electrified his audience. He waved before their dazzled eyes an “idea with a sword” which showed them how France could win. Its essence was the offensive à outrance, offensive to the limit. Only this could achieve Clausewitz’s decisive battle which “exploited to the finish is the essential act of war” and which “once engaged, must be pushed to the end, with no second thoughts, up to the extremes of human endurance.” Seizure of initiative is the sine qua non. Preconceived arrangements based on a dogmatic judgment of what the enemy will do are premature. Liberty of action is achieved only by imposing one’s will upon the enemy. “All command decisions must be inspired by the will to seize and retain the initiative.” The defensive is forgotten, abandoned, discarded; its only possible justification is an occasional “economizing of forces at certain points with a view to adding them to the attack.