by no means followed that it
could be forced for the second time in face of a concentrated enemy,
who would have had time to recover his morale and supply his losses.
McClellan, so long as the Confederates remained in Maryland, had
evidently made up his mind to attack. But if Maryland was evacuated
he would probably content himself with holding the line of the
Potomac; and, in view of the relative strength of the two armies, it
would be an extraordinary stroke of fortune which should lay him open
to assault. Lee and Jackson were firmly convinced that it was the
wiser policy to give the enemy no time to reorganise and recruit, but
to coerce him to battle before he had recovered from the defeat which
he had sustained on the heights above Bull Run. To recross the
Potomac would be to slight the favours of fortune, to abandon the
initiative, and to submit, in face of the vast numbers of fresh
troops which the North was already raising, to a defensive warfare, a
warfare which might protract the struggle, but which must end in the
exhaustion of the Confederacy. McClellan's own words are the
strongest justification of the views held by the Southern leaders:--

"The Army of the Potomac was thoroughly exhausted and depleted by the
desperate fighting and severe marching in the unhealthy regions of
the Chickahominy and afterwards, during the second Bull Run campaign;
its trains, administrative services and supplies were disorganised or
lacking in consequence of the rapidity and manner of its removal from
the Peninsula, as well as from the nature of its operations during
the second Bull Run campaign.

"Had General Lee remained in front of Washington (south of the
Potomac) it would have been the part of wisdom to hold our own army
quiet until its pressing wants were fully supplied, its organisation
was restored, and its ranks were filled with recruits--in brief,
until it was prepared for a campaign. But as the enemy maintained the
offensive, and crossed the Upper Potomac to threaten or invade
Pennsylvania, it became necessary to meet him at any cost,
notwithstanding the condition of the troops, to put a stop to the
invasion, to save Baltimore and Washington, and throw him back across
the Potomac. Nothing but sheer necessity justified the advance of the
Army of the Potomac to South Mountain and Antietam in its then
condition. The purpose of advancing from Washington was simply to
meet the necessities of the moment by frustrating Lee