2.  By retreating across the Potomac, in accordance with General Longstreet’s suggestion, Lee would certainly have avoided all chances of disaster.  But, at the same time, he would have abandoned a good hope of ending the war.  The enemy would have been fully justified in assuming that the retrograde movement had been made under the compulsion of his advance, and the balance of morale have been sensibly affected in favour of the Federals.  If the Potomac had once been placed between the opposing forces, McClellan would have had it in his power to postpone an encounter until his army was strongly reinforced, his raw regiments trained, and his troops rested.  The passage of the river, it is true, had been successfully forced by the Confederates on September 5.  But it 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