THE month of September, 1862, was a period of strong excitement and profound anxiety on both sides of the vague and shifting line which divided the loyal North from the misguided but courageous South. During the latter part of August Gen. Pope had been overwhelmed with disaster, and what was left of his heroic army was driven within the fortifications erected for the defence of Washington. Apparently the South had unbounded cause for exultation. But a few weeks before their capital had been besieged by an immense army, while a little to the north, upon the Rappahannock, rested another Union army which, under a leader like Stonewall Jackson, would have been formidable enough in itself to tax Lee's skill and strength to the utmost. Except in the immediate vicinity of the capital and Fortress Monroe scarcely a National soldier had been left in Virginia. The Confederates might proudly claim that the generalship of Lee and the audacity of Jackson had swept the Northern invaders from the State. Even more important than the prestige and glory won was the fact that the Virginian farmers were permitted to gather their crops unmolested. The rich harvests of the Shenandoah Valley and other regions, that had been and should have been occupied by National troops, were allowed to replenish the Confederate granaries. There were rejoicings and renewed confidence in Southern homes, and smiles of triumph on the faces of sympathizers abroad and throughout the North. But the astute leaders of the Rebellion were well aware that the end had not yet come, and that, unless some bold, paralyzing blow was struck, the struggle was but fairly begun. In response to the request for more men new armies were springing up at the North. The continent shook under the tread of hosts mustering with the stern purpose that the old flag should cover every inch of the heritage left by our fathers. Therefore, Lee was not permitted to remain on the defensive a moment, but was ordered to cross the Potomac in the rear of Washington, threatening that city and Baltimore. It was supposed that the advent of a Southern army into Maryland would create such an enthusiastic uprising that thinned ranks would be recruited, and the State brought into close relation with the Confederate Government. These expectations were not realized. The majority sympathized with Barbara Frietchie, "Bravest of all in Frederick town," rather than with their self-styled deliverers; and Lee lost more by desertion from his own ranks than he gained in volunteers. In this same town of Frederick, by strange carelessness on the part of the rebels, was left an order which revealed to McClellan Lee's plans and the positions which his divided army were to occupy during the next few days. Rarely has history recorded such opportunities as were thus accidentally given to the Union commander.