While we rested, the enemy was bringing up reinforcements from the direction of Richmond. Very early in the morning the siege guns on Stafford Heights, opposite the town, sent some shells screaming across the valley to the heights of Marye's Hill, giving the alarm to those in the town and to those who had so recently left it. Lines of rebels were seen all along the outskirts of the town and on the crests above. Fifteen thousand confederate troops were between the Sixth corps and Fredericksburgh Heights. The surgeons immediately prepared to send the wounded across the river, but, supposing that to accomplish the whole before the rebels should take possession of the town would be impossible, made every preparation for being themselves taken prisoners. A small detachment of Gibbon's division still guarded the town, but nearly all his troops had recrossed the river and were on Stafford Heights. But the small force in the town seemed sufficient to convey to the rebels the impression that it was well guarded, for they made no attempt to seize the immense amount of hospital stores which was at their mercy, or to molest the wounded or the surgeons.

The Sixth corps was now in a critical position; its communications entirely cut off, and surrounded by hosts of the enemy. The corps was sandwiched between the rebels on the heights and Lee's whole army; while on its left was a strong force, and on its right an impassable river. Dispositions were at once made to meet the emergency.

Brooks' division was drawn back, and Howe's, still in the rear, changed front and quickly extended the line of battle to the river, so as to include Banks' Ford, six miles above the city, over which communications were at once established.

The whole of Early's rebel division occupied the crest of Marye's and Cemetery Hills; the divisions of Anderson and McLaws were on our flank; and the brigades of Hays, Hoke and Lawton, supported by Lee's whole army, were in our rear. We were in the vicinity of Salem Church, and our only line of retreat was upon the road leading to Banks' Ford.

The first demonstration of the rebels, on the morning of the 4th, was against the position held by Neill's brigade. A company from the Seventh Maine, and two companies from the Forty-ninth New York, in conjunction with a part of Martin's battery, and supported by the remaining companies of the Forty-ninth, gallantly repulsed and routed a whole brigade of rebels, capturing two hundred prisoners, and the colors of the Fifty-eighth Virginia regiment; which last trophy was borne off by the men of the Forty-ninth, and was the second stand of colors taken by that gallant brigade in this engagement, the Seventy-seventh having captured the other.

The day wore away with little fighting till five o'clock. General Howe had so disposed his troops as to occupy two positions.

In front was the Third brigade, holding a crest which overlooked a ravine through which the rebels must pass. Behind the brigade was another ravine, in which was a thin skirt of woods. In rear of this second ravine, and behind a swell of ground, the Vermont brigade was strongly posted, forming the second line of battle. There were in each of these two brigades about three thousand men.

Now came the most fearful struggle of the campaign. At five o'clock the rebel hordes came, with deafening yells, upon the division. The divisions of Early, Anderson and McLaws rushed upon the single brigade of less than three thousand men, massing their troops in the ravine, and charging with impetuous fury. But the noble regiments heroically withstood the shock, the Germans of the Twentieth only going to the rear in confusion. The stubborn resistance of the brigade prevented the rebels from piercing our lines, and cutting off our retreat, and thus, by its gallantry, enabled the corps to cross at Banks' Ford. But one thousand men—more than one-third of the brigade—fell on that crest. Colonel Van Houghton, of the Twenty-first New Jersey, was mortally wounded, and many other choice spirits were among the fallen. General Neill was injured by the fall of his horse, which was shot. General Howe now ordered the brigade to fall back, and the decimated regiments left the front line, and fell behind the strong position held by the Vermonters. The rebels, thinking this a retreat, followed with yells of exultation, but were met by the second line of battle, which, from its position behind the swell of ground, was concealed, with a murderous fire, which sent them reeling back to the cover of the first ravine. Their charge had inflicted little damage upon the Union line. It was now nearly dark, and the reception which the rebels had received had so completely routed and broken them, that they made no further attempt upon our lines.

About nine o'clock, the division was ordered to fall back to Banks' Ford, now two miles distant from us. We fell back quietly, and found that the other divisions had preceded us, and were snugly behind rifle pits. They had fallen back as soon as it was dark, leaving the Second division to cover the retreat.

Meantime, comparatively little fighting had been done by the other divisions, though a constant skirmish was kept up, and in the evening the confederates managed to get in the rear of a part of the picket of the Light division, capturing a large number of prisoners from the Forty-third and Thirty-first New York, and Sixty-first Pennsylvania.