At the same time Moltke had worked out the conditions of the march and supply of an army. Only one army corps could be moved along one road in the same day; to put two or three corps on the same road meant that the rear corps could not be made use of in a battle at the front. Several corps stationed close together in a small area could not be fed for more than a day or two. Accordingly, he inferred that the essence of strategy lay in arrangements for the separation of the corps for marching and their concentration in time for battle. In order to make a large army manageable, it must be broken up into separate armies or groups of corps, each group under a commander authorized to regulate its movements and action subject to the instructions of the commander-in-chief as regards the direction and purpose of its operations.