Though Hooker's plan promised excellent results here, Meade was fearful lest Lee should cross the Susquehanna, and take Harrisburg before he could be stopped. To prevent this the army must be pushed forward. Meade, therefore, at once drew back the left wing toward Frederick, thus giving up that plan in favor of one which he himself had formed; namely, of throwing the army out more to the northeast, the better to cover Baltimore from attack, should that be Lee's purpose, as Meade more than suspected. Selecting Westminster, therefore, as his base from this time forth, and the line of Big Pipe Creek, a little to the north of that place, as his battle-ground, Meade now set most of the army in motion in that direction, leaving Frederick to the protection of a rear-guard. [Sidenote: Left Flank Forward.] [Sidenote: Right Flank refused.] The army now marched with its left wing thrown forward toward South Mountain, Buford's cavalry toward Fairfield, to clear that flank, the First and Eleventh Corps toward Emmettsburg, the Third and Twelfth toward Middleburg, the Fifth to Taneytown, the Second to Uniontown, and the Sixth, on the extreme right, to New Windsor. Two other divisions of Union cavalry, Kilpatrick's and Gregg's, marched one on the right flank, the other in front, with orders to keep the front and flanks of the army well scouted and protected. It will be seen from this order of march that, in proportion as they went forward, Buford's cavalry, with the three infantry corps forming the left wing, were approaching the enemy's main body at Chambersburg. South Mountain was, therefore, the wall behind which the two contending armies were playing at hide-and-seek.[26] [Sidenote: Lee hears Meade is coming.] Lee had only just given orders for his whole force to move on Harrisburg, when, late in the night of the 28th, a scout brought news to him of the Union army being across the Potomac, and on the march toward South Mountain.[27] This report could not fail to throw the Confederate headquarters into a fever of excitement, ignorant to that hour of that army's being across the Potomac. The mystery was cleared up at last. In a moment the plan of campaign was changed.[28] Lee soon said to some of the officers about him, "To-morrow, gentlemen, we will not move to Harrisburg as we expected, but will go over to Gettysburg and see what General Meade is about." [Sidenote: March on Gettysburg begun.] By placing himself on the direct road to Baltimore, Lee's purpose of first drawing the Union army away from his line of retreat, and of then assailing it on its own, stands fully revealed. The previous orders were therefore countermanded on the spot. Hill and Longstreet were ordered from Chambersburg to Gettysburg,[29] Ewell was called back from Carlisle, and Early from York. [Sidenote: Faulty Tactics.]