The Battle of Mechanicsville, also known as the battle of Beaver Dam Creek. which opened the Confederate offensive of the Seven Days on June 26, 1862 was a tactical fiasco and defeat for the Army of Northern Virginia and a strategic defeat for the Army of the Potomac.
Lee’s plan to attack Porter’s V Corps, the only corps of the Army of the Potomac north of the Chickahominy, defeat it and turn the right flank of the Army of the Potomac went badly awry in execution. Beginning the poor performance that would plague him throughout the Seven Days, Jackson was four hours late in attacking the north flank of Porter’s corps. Instead, AP Hill attacked with his division in futile and bloody frontal assaults which were easily repulsed by Porter. After Jackson’s arrival, he bivouacked his men, although the sounds of a major attack were clear. AP Hill renewed his attacks, reinforced by DH. Hill’s brigade, although Lee had ordered no more attacks and was again bloodily repulsed. Confederate casualties were 1461 with Union casualties half this number. So a humiliating tactical defeat for the Confederates marked by an inept inability on the part of Lee to put forward a coordinated attack.
However, McClellan turned this day of Confederate defeat into one of victory. Assuming, as he always did, that he was heavily outnumbered, and fearing that Jackson was positioned to march into his rear and cut off his supply lines, McClellan ordered Porter to retreat, and decided to abandon his supply line which relied upon the rail line north of the Chickahominy, the York and Richmond Railroad, and to rely upon a supply line by water up the James River. This decision meant that he was going to have to withdraw from his positions in front of Richmond and retreat down the Peninsula. Few defeats have reaped such rich rewards as Mechanicsville did for the Confederacy. Here is General Lee’s report on the battle of Mechanicsville which was written on March 6, 1863:
BATTLE OF MECHANICSVILLE.
According to the general order of battle, a copy of which is annexed, General Jackson was to march from Ashland on the 25th in the direction of Slash Church, encamping for the night west of the Central Railroad, and to advance at 3 a.m. on the 26th and turn Beaver Dam. A. P. Hill was to cross the Chickahominy at Meadow Bridge when Jackson’s advance beyond that point should be known and move directly upon Mechanicsville. As soon as the Mechanicsville Bridge should be uncovered Longstreet and D. H. Hill were to cross, the latter to proceed to the support of Jackson and the former to that of A. P. Hill. The four commands were directed to sweep down the north side of the Chickahominy toward the York River Railroad, Jackson on the left and in advance, Longstreet nearest the river and in the rear. Huger and Magruder were ordered to hold their positions against any assault of the enemy, to observe his movements, and follow him closely should he retreat. General Stuart, with the cavalry, was thrown out on Jackson’s left to guard his flank and give notice of the enemy’s movements. Brigadier-General Pendleton was directed to employ the Reserve Artillery, so as to resist any approach of the enemy toward Richmond, to superintend that portion of it posted to aid in the operations of the north bank, and hold the remainder ready for use when it might be required.
In consequence of unavoidable delays the whole of General Jackson’s command did not arrive at Ashland in time to enable him to reach the point designated on the 25th. His march on the 26th was consequently longer than had been anticipated, and his progress being also retarded by the enemy, A. P. Hill did not begin his movement until 3 p.m., when he crossed the river and advanced upon Mechanicsville. After a sharp conflict he drove the enemy from his intrenchments, and forced him to take refuge in his works on the left bank of Beaver Dam, about 1 mile distant. This position was a strong one, the banks of the creek in front being high and almost perpendicular, and the approach to it over open fields, commanded by the fire of artillery and infantry intrenched on the opposite side. The difficulty of crossing the stream had been increased by fellling the woods on its banks and destroying the bridges. Jackson being expected to pass Beaver Dam above and turn the enemy’s right, a direct attack was not made by General Hill. One of his regiments on the left of his line crossed the creek to communicate with Jackson and remained until after dark, when it was withdrawn. Longstreet and D. H. Hill crossed the Mechanicsville Bridge as soon as it was uncovered and could be repaired, but it was late before they reached the north bank of the Chickahominy. D. H. Hill’s leading brigade, under Ripley, advanced to the support of the troops engaged, and at a late hour united with Pender’s brigade, of A. P. Hill’s division, in an effort to turn the enemy’s left; but the troops were unable in the growing darkness to overcome the obstructions, and after sustaining a destructive fire of musketry and artillery at short range were withdrawn. The fire was continued until about 9 p.m., when the engagement ceased. Our troops retained the ground on the right bank, from which the enemy had been driven. Ripley was relieved at 3 a.m. on the 27th by two of Longstreet’s brigades, which were subsequently re-enforced. In expectation of Jackson’s arrival on the enemy’s right the battle was renewed at dawn, and continued with animation for about two hours, during which the passage of the creek was attempted and our troops forced their way to its banks, where their progress was arrested by the nature of the stream. They maintained their position while preparations Were being made to cross at another point nearer the Chickahominy, Before they were completed Jackson crossed Beaver Dam above, and the enemy abandoned his intrenchments and retired rapidly down the river, destroying a great deal of property, but leaving much in his deserted camps.