no time is this more sensibly felt by every one than on a retreat. The intention always is, that the wings in case of extremity should close upon the centre; and if, on account of subsistence and roads, the retreat has to be made on a considerable width (of country), still the movement generally ends by a concentration on the centre. If we add to these considerations also this one, that the enemy usually advances with his principal force in the centre and with the greatest energy against the centre, we must perceive that the rear guard of the centre is of special importance.
Accordingly, therefore, a special corps should always be thrown forward as an advanced guard in every case where one of the above relations occurs. These relations almost fall to the ground if the centre is not stronger than the wings, as, for example, Macdonald when he advanced against Blücher, in Silesia, in 1813, and the latter, when he made his movement towards the Elbe. Both of them had three corps, which usually moved in three columns by different roads, the heads of the columns in line. On this account no mention is made of their having had advanced guards.