The Third and Fifth Corps will form the centre grand division, and will be commanded by Major-General Joseph Hooker.
The Eleventh Corps, with such others as may hereby be assigned to it, will constitute a reserve force, under the command of Major-General F. Sigel.
Assignments of cavalry and further details will be announced in future orders.
By command of Major-General BURNSIDE.
S. Williams, A. A.-G.
Meanwhile the mass of General Lee’s forces retired to Gordonsville. On the 16th the forces of General Burnside began to move for Fredericksburg, as had been previously determined in consultation on the 12th between Generals Halleck and Burnside. On the 15th the evacuation of Warrenton and the adjacent places was commenced, and by the morning of the 18th it was entirely completed. The advance was led by General Sumner. At the same time supplies were sent to Acquia Creek, and the repairs of the railroad track to Fredericksburg commenced, and the army concentrated at Falmouth, opposite Fredericksburg.
The march to Richmond was to be made by the route from Fredericksburg. This city is on the south bank of the Rappahannock, and sixty-five miles distant from Richmond. It is connected with the latter place by a railroad, of which there is a double line nearly to Hanover Junction, twenty-three miles from Richmond. The railroad crosses the Matapony river at Milford, thirty-seven miles from Fredericksburg, and the Pamunkey, twenty-five miles from Richmond, besides a number of smaller streams. Between Falmouth, where the Federal army concentrated, and Richmond, there are two main and two minor lines of defence. The first that of the Rappahannock river. Above Falmouth its abrupt banks, which are lined with high hills, difficult of access, and its narrow fords and rocky bottom render a rapid crossing for a large force almost impossible. Below, the valley of the river expands, spreading often into spacious plains, while the winding course of the stream forms numerous necks of land, easily commanded from the north side, and giving secure crossing places, and ample ground for the formation of troops. At Fredericksburg the north commands the south bank, and much of the distance, which is a mile and a half, to the frowning hills or table land beyond. But these heights equally command this intermediate plain, and are unassailable in front except by infantry. Next in the rear, and twelve miles distant, is the line of the Po river and Stannard’s Marsh, which is hardly available except to hold a pursuing foe in check. The North Anna is about forty miles from the Rappahannock, and affords another principal line of defence. It is a deep and rapid stream, with a narrow valley. The table-land on its north bank is about one hundred feet above the bed of the river, and about one hundred and fifty feet on the south bank. The extension of its line after it turns to join the South Anna, and becomes the Pamunkey, presents scarcely less obstacles than the river itself, so well is the ground guarded by swamps and flanked by streams. The last and a minor line of defence is the South Anna river, with the southern commanded by the northern bank, and too near the North Anna for a second formation by a force that has been badly defeated. Numerous small streams parallel to the line of advance present suitable points for resistance, and protect foes attacking the line communication, while the bridges over them are weak points necessary to be securely guarded.
By the 20th a considerable force had reached Falmouth. General Sumner on the next day sent a summons to surrender, which elicited a correspondence from Mayor Slaughter, showing that the town was at the mercy of the combatants, and beyond the control of the city authorities.
As General Burnside’s army concentrated on the north bank, General Lee’s forces concentrated on the heights in the rear of Fredericksburg. Had the pontoon bridges been at hand when the advance reached Falmouth, the line of the Rappahannock would have been taken without opposition. Then, with proper supplies and bridges, thirty of the sixty miles to Richmond would have been placed within the reach of General Burnside, and perhaps a lodgment have been effected on the banks of the North Anna. Nearly thirty days elapsed before the pontoons arrived and the bridges were completed.
It was the design of General Burnside that the pontoons should leave Alexandria on November 11, and arrive at Falmouth at the same time with the advance of his army. The right grand division reached Falmouth on November 17. The pontoons left Alexandria on November 19, and arrived at Fredericksburgh after the movements of General Burnside had not only become known, but after General Lee had advanced his forces from Gordonsville to the heights in the rear of Fredericksburg, and had fortified them. They were not used until the night of December 10, owing to material changes in the plan of the commander-in-chief, necessitated by new movements of the enemy.