“In seeking to upset the enemy's balance, a commander must not lose his own balance. He needs to have the quality, which Voltaire described as the keystone of Marlborough's success– 'the calm courage in the midst of tumult, that serenity of soul in danger, which the English call a cool head.' But to it he must have the quality for which the French have found the most aptly descriptive phrase–'le sense du practible.' The sense of what is possible, and what is not possible–tactically and administratively. The combination of both [of] these two 'guarding' qualities might be epitomized as the power of cool calculation. The sands of history are littered with wrecks of finely conceived plans that expired for want of this ballast.”