He never assembled much more than 60,000 men from that point on, and he was limited by his own superiors and his own preference to operating in a narrow albeit important theater.
His only choice after Gettysburg was to hold on in the hopes of foreign intervention, which had no chance of coming anymore.
that last chance came in APR 65, when he failed to break the ANV & the other major CSA forces into guerrilla bands & fight on, until the north decided to QUIT.
The quitters among the Union had already been purged from both military and political life. Vallandigham had lost all credibility with one of the most ill-timed speeches in political history and McClellan was powerless. Grant was not a quitter, nor was Sherman, nor was Sheridan.
Lincoln was not a quitter either, nor was Seward, nor was Stanton, nor was Welles. Every milquetoast that tied the Union's hands behind its back was scoured out of the administration and out of the command - they were deadenders all in 1865.
Sherman was already operating on a total war footing by April 1865 - his men had become past masters at hunting down and destroying Rebel guerrilla units. Grant could have quickly learned that art as well.
The very first guerrilla raid against a Northern city would have been the last one.
fwiw, Lee did NOT have to WIN;he simply had to avoid final DEFEAT.
The entire point of the Confederacy was to hold and govern land, not to operate as a secret Mafia. Terrorism was not only beneath Lee's dignity, it did not serve his purposes at all.
Lee needed to win on the battlefield to avoid defeat. And by Appomattox he had done about 99% of the winning his resources enabled him to do.
trust me, in about DEC 1975 or perhaps MUCH SOONER, the civilians in the north would have done ANYTHING to end the war against the north-anything, especially if the guerrillas had started burning NORTHERN cities (say one a month???).
The record of the Civil War shows that such provocations only made the North more determined to punish the Confederates, not less. Antietam and Gettysburg proved that in spades. A more accurate picture is that between July '61 and September '62 there were plenty of Northerners who questioned whether the war was worthwhile. That was the window of opportunity for the cowards and the defeatists of the Union, helped along by the incompetence of the general staff and the disloyalty of one faction of Northern Democrats.
After Antietam and the successful November '62 elections for the GOP, the Peace Democrats were routed as a viable political faction.
After the Overland Campaign and the election of '64 the entire Democrat party, defeatist and Unionist, held less than 20% of the seats in Congress.
80% of the North was backing Grant and Sherman unconditionally and a guerrilla raid on any Northern city would have provoked red rage, not fear.
fwiw, i personally wrote most of the "rear area protection doctrine" in the late '70s & early '80s (TWO 2-year tours on the faculty) for USAMPS,after we learned the lesson of RVN.
a country CANNOT EVER defeat of well-supported (by the civilian population) guerrilla movement, even with helicopters, gunships,advanced weaponry. period. end of story.(btw, may i remind you that since the 19th Century, that SPAIN, JAPAN, the USA & the PHILLAPINE government have tried & FAILED (miserably, btw) to "put down" the Huk's resistance??? fyi, the Huks NEVER had more than 10K active fighters, but they STILL hold much of "the back country".)
had Lee decided to do precisely what i said, the north would have given up & left dixie within ten years or less, especially if EVERY major industrial city in the north started BURNING. (may i remind you what the Chicago fire did??) YEP, anyone who got "caught" would have faced "a short trial & a quick rope or firing squad".) nonetheless, such guerrilla acts NEVER fail for want of volunteers!!!
fwiw, had the union army decided to "take it out on" the southern civilian population, that too would have backfired on the union & solidified dixie morale/support for the "martyrs".
in the end, the north would have "just gone home" & dixie would have been forever FREE.
free dixie,sw