deep
ravine, so that the left wing was isolated from the centre and right.
This vicious disposition did not escape the penetrating eye of
Napoleon, who attacked their isolated wing with superior forces and
routed it completely, with the capture of 10,000 prisoners, before any
assistance could arrive. The task of creating lateral communications,
if none exist, is of the utmost importance, as they enable a commander
to achieve the primary object of every military manoeuvre, to meet the
enemy with superior forces at the desired point.

(ix) _There should be good lines of withdrawal_, and these should be
horizontal, or only slightly oblique, to {90} the main position, and
not parallel with the general alignment. This is a point of the first
importance, for if the Lines of Communication lead straight to the rear
a force that is overwhelmed by the attack can withdraw to selected
positions and towards its base, if it can keep the line intact and
prevent its flanks being turned. A wide base, with alternative lines
of approach, is of the greatest value, and when there is undue risk of
the Lines of Communication to a base being intercepted, an alternative
base, with lines of withdrawal thereto from the unexposed flank, is an
acceptable safeguard, as the defence can be protracted while the
withdrawing force concentrates upon the changed base. Such a change of
base was effected by Marshal French during the _Retreat from Mons_, and
amongst many historical examples may be quoted General McClellan's
transfer of the _Army of the Potomac_ from the York to the James River
in July, 1862, during the _Seven Days' Battle around Richmond_.
General Grant changed his base no fewer than five times during the
_Campaign in the Wilderness_ (May, 1864), from Washington to Orange and
Alexandria Railroad, then to Fredericksburg on the Rappahannock, then
to Port Royal, further east on that river, then to White House on the
Pamunkey (a branch of the York River), and finally to the James River.
"His army was always well supplied, even his enormous numbers of
wounded were carried straight away to the base and thence to
Washington, without any difficulty, and he had no obstacles whatever to
fight against as regards either feeding his army or keeping up the
supply of ammunition" (Henderson). In withdrawing a defeated wing it
may even be advantageous to rally the troops at a point distant from
the field of battle, and to cause the pursuer, uncertain as