Nevertheless, on the night of the 13th disaster threatened the Confederates.  Harper’s Ferry had not yet fallen, and, in addition to the cavalry, D.H.  Hill’s division was alone available to defend the passes.  Lee, however, still relying on McClellan’s irresolution, determined to hold South Mountain, thus gaining time for the reduction of Harper’s Ferry, and Longstreet was ordered back from Hagerstown, thirteen miles west of Boonsboro’, to Hill’s assistance.

September 14.

On the same night Jackson, at Halltown, opened communications with McLaws and Walker, and on the next morning (Sunday) he made the necessary arrangements to ensure combination in the attack.  The Federal lines, although commanded by the Maryland and Loudoun Heights to the north and east, opposed a strong front to the south and west.  The Bolivar Heights, an open plateau, a mile and a quarter in length, which has the Potomac on the one flank and the Shenandoah on the other, was defended by several batteries and partially intrenched.  Moreover, it was so far from the summits occupied by McLaws and Walker that their guns, although directed against the enemy’s rear, could hardly render effective aid; only the extremities of the plateau were thoroughly exposed to fire from the heights.

In order to facilitate communication across the two great rivers Jackson ordered a series of signal stations to be established, and while his own batteries were taking up their ground to assail the Bolivar Heights he issued his instructions to his colleagues.  At ten o’clock the flags on the Loudoun Heights signalled that Walker had six rifled guns in position.  He was ordered to wait until McLaws, who was employed in cutting roads through the woods, should have done the same, and the following message explained the method of attack:—­

“General McLaws,—­If you can, establish batteries to drive the enemy from the hill west of Bolivar and on which Barbour’s House is, and from any other position where he may be damaged by your artillery.  Let me know when you are ready to open your batteries, and give me any suggestions by which you can operate against the enemy.  Cut the telegraph line down the Potomac if it is not already done.  Keep a good look-out against a Federal advance from below.  Similar instructions will be sent to General Walker.  I do not desire any of the batteries to open until all are ready on both sides of the river, except you should find it necessary, of which you must judge for yourself.  I will let you know when to open all the batteries.

“T.J.  Jackson,

“Major-General Commanding."* (* Report of Signal Officer, O.R. volume 19 part 1 page 958.)

About half-past two in the afternoon McLaws reported that his guns were up, and a message “to fire at such positions of the enemy as will be most effective,” followed the formal orders for the co-operation of the whole force.

“Headquarters, Valley District,