"Everything in war is very simple, but the simplest thing is very difficult. These difficulties accumulate and produce a friction which no man can imagine exactly who has not seen war. ... Countless minor incidents — the kind one can never really foresee — combine to lower the general level of performance. So that one always falls short of the intended goal. ... The military machine ... is basically very simple and easy to manage. But we should bear in mind that none of its components is of one piece: each part is composed of individuals, every one of whom retains his potential of friction.... A battalion is made up of individuals, the least important of whom may chance to delay things and sometimes make them go wrong. ...