Lee manoeuvred to draw McClellan away from Washington and Baltimore,
that he might attack them before the Union commander could return to
their defense. Lee left Frederick on September 10th, after Jackson had
started for Harper's Ferry, and, marching by South Mountain, aimed for
Boonsboro'. Stuart and his cavalry remained east of the mountains to
watch McClellan, who was advancing with every possible precaution. Lee
expected Harper's Ferry would fall on the 13th, but the surrender did
not take place until two days later. The Confederate army being divided,
McClellan tried to take advantage of the fact, hoping to save Colonel
Miles at Harper's Ferry. It did not take Lee long to perceive from the
actions of the Union commander that in some way he had learned of his
plans.

It would not be interesting to give the details of the many manoeuvres
by each commander, but before long Lee saw he could not hold his
position at South Mountain, and he retreated toward Sharpsburg, near the
stream of water known as Antietam Creek. He was thus on the flank of any
Federal force that might attempt to save Harper's Ferry. Naturally he
held the fords of the Potomac, so that in case of defeat the way to
Virginia was open.

[Illustration: GENERAL LEE'S INVASION OF THE NORTH.

The Confederate army under General Lee twice invaded the north. The
first invasion was brought to a disastrous end by the Battle of
Antietam, September 17, 1862. The second invasion ended with greater
disaster at Gettysburg, July 1-3, 1863. Gettysburg was the greatest and
Antietam the bloodiest battles of the war.]

Still Lee and Jackson were separated by a wide stretch of mountain,
river, and plain, and McClellan was aware of the fact. He had the
opportunity to cut off each division in detail, but lacked the nerve and
dash to do it. There were subordinates in the Army of the Potomac who
yearned for just such a chance, but McClellan's timidity and excessive
caution deprived him of another golden opportunity, as it had done
before and was soon to do again.

The position of Lee was among a range of hills, which, following the
form of a crescent, extended from the lower point of Antietam Creek to a
bend in the Potomac. Jackson was straining every nerve to join Lee, but
his men were taxed beyond endurance, and many of them fell by the
roadside from utter exhaustion, only a portion reaching Sharpsburg on
the 16th. The full Confederate army did not exceed 40,000, while