Napoleon: A Life

by Andrew Roberts

Napoleon to divide his army into units of 20,000 to 30,000 men, sometimes up to 40,000, and to train them intensely. Each corps was effectively a mini-army, with its own infantry, cavalry, artillery, staff, intelligence, engineering, transport, victualling, pay, medical and commissary sections, intended to work in close connection with other corps. Moving within about one day’s march of each other, they allowed Napoleon to swap around the rearguard, vanguard or reserve at a moment’s notice, depending on the movements of the enemy. So, in either attack or retreat, the whole army could pivot on its axis without confusion. Corps could also march far enough apart from each other not to cause victualling problems in the countryside. Each corps needed to be large enough to fix an entire enemy army into position on the battlefield, while the others could descend to reinforce and relieve it within twenty-four hours, or, more usefully, outflank or possibly even envelop the enemy.