McClellan had failed to take Richmond, and although his army had fought hard battles on the Chickahominy and at Malvern Hill, it won no victories that bore fruits save in lists of dead and wounded, and his army, on being withdrawn from the James in August, 1862, did not effectively sustain General John Pope at the Second Bull Run. On being given command of the combined Union forces at and about Washington, McClellan again had a large and splendidly equipped army under him. He at first exhibited some energy in moving it into Maryland after Lee, but by his extreme caution and delays suffered Harper's Ferry to be taken (September 15, 1862), with 10,000 men and an immense supply of arms and stores, and finally, when fortune smiled on his army at Antietam, he allowed it to lay quietly on its arms a whole day and long enough to enable Lee to retreat across the Potomac, where he was permitted to leisurely withdraw, practically unmolested, southward. The critical student of the battle of Antietam will learn of much desperate fighting on both sides, with no clearly defined general plan of conducting the battle on either side. As Lee fought on the defensive, he could content himself with conforming the movements of his forces to those of the Union Army. Stonewall Jackson, after maintaining a short, spirited battle against Hooker's corps, withdrew his corps from the engagement at seven o'clock in the morning and did not return to the field until 4 P.M.( 1) Generally the Union Army was fought by divisions, and seldom more than two were engaged at the same time, often only one. In this way some of the divisions, for want of proper supports, were cut to pieces, and others were not engaged at all. Acting on interior lines, Lee was enabled to concentrate against the Union attacks and finally to repulse them. Notwithstanding this mode of conducting the battle, the Confederate Army was roughly handled and lost heavily. General Ambrose E. Burnside late in the day succeeded in crossing Antietam Creek at the Stone Bridge and planting himself well on the Confederate right flank. McClellan also had, at night, many fresh troops ready and eager for the next day's battle. Considerable parts of his army had not been engaged, and reinforcements came. The two armies confronted each other all day on the 18th, being partly engaged in burying the dead, as though a truce existed, and at night Lee withdrew his army into Virginia.( 2)