/HFWXUH $QWLHWDP²7KH&LYLO:DU¶V%ORRGLHVW'D\
vigorously reorganized the army, enforced modern drill, and greatly
improved both its discipline and morale.x Like Lee, he was popular with the soldiers, who appreciated
his constant and energetic efforts to improve their conditions.
He also applied his industry to erecting a powerful network of
IRUWL¿FDWLRQVDURXQG:DVKLQJWRQWKDWZHUHVRH[WHQVLYHDQGZHOO
made that the Confederates would never make a serious effort to
break through them.x Yet McClellan suffered substantial weaknesses as a general: He
persisted in vastly overestimating the numbers of his foes, which led
him to be overly cautious and slow to attack. He repeatedly failed to
H[SORLWRSSRUWXQLWLHVRQWKHEDWWOH¿HOGNHHSLQJODUJHFRQWLQJHQWVRI
his troops in reserve when they would have been better employed in
attacking the enemy.x 7KHVH GH¿FLHQFLHV FDXVHG KLP WR EH UHOLHYHG RI FRPPDQG EXW
when his successor was thrashed at the Second Battle of Bull Run,
Lincoln turned to McClellan to rebuild the broken army. Thus,
when Lee followed up the victory at Second Bull Run with his
invasion of Maryland, it fell to McClellan to oppose him.The Battle
x At the outset, McClellan fell into a rare opportunity. Lee had written
up his plans for the campaign, including detailed instructions and
timetables for the movements of each segment of his army—four
groups that would converge on a Union garrison at Harpers Ferry—
in a document labeled “Special Order 191.” Copies of the order
were sent to each of his principal commanders, but one was found
lying on the ground by a group of Union soldiers and quickly made
its way up the chain of command to McClellan.x The value of this intelligence was undermined by McClellan’s
habitual caution. He squandered his opportunity by deploying
his army too sluggishly to catch the elements of Lee’s army and
destroy them, with the result that Harpers Ferry fell to Stonewall