Porter withdrew his corps safely to Gaines Mill, with the exception of Company F ("The Hopewell Rifles") of the 8th Pennsylvania Reserve Regiment who did not receive the orders to retreat.

After the Battle of Seven Pines, on May 31 and June 1, McClellan and the Army of the Potomac sat passively at the outskirts of Richmond for almost a month.

Gen. Porter was north of the river near Mechanicsville in an L-shaped line running north–south behind Beaver Dam Creek and southeast along the Chickahominy.

It was a risky plan that required careful execution, but Lee knew that he could not win in a battle of attrition or siege against the Union army.

Stuart's forces burned a couple of Union supply ships and was able to report much of McClellan's army's strength and position to Gen. Lee.

McClellan was aware of Jackson's arrival and presence at Ashland Station, but did nothing to reinforce Porter's vulnerable corps north of the river.

[7] Lee's plan called for Jackson to begin the attack on Porter's north flank early on June 26.

Hill's Light Division was to advance from Meadow Bridge when he heard Jackson's guns, clear the Union pickets from Mechanicsville, and then move to Beaver Dam Creek.

Lee expected Jackson's flanking movement to force Porter to abandon his line behind the creek, and so A. P. Hill and Longstreet would not have to attack Union entrenchments.

Gen Lawrence O'Bryan Branch's brigade, which was placed off to the north to link up with Jackson, entered Mechanicsville and skirmished with George McCall's Union division, deployed around the town.

McCall fell back to an easily defensible spot on the opposite side of Beaver Dam Creek.

Hill's 11,000 men, most of them green regiments who had never fired a shot in battle, launched a series of futile attacks over the next few hours.

Directing his troops, John Reynolds gestured at the oncoming mass of Confederates and told a staffer "There they come like flies on a piece of gingerbread."

Hill had 24 guns with him, he made no attempt to use massed artillery fire to counter the Union gunners, instead sending individual batteries in support of the infantry, most of which were quickly put out of action by enemy shelling.

[11] Some of Anderson's men managed to get across the creek and momentarily threaten Reynolds's position, however he was reinforced by Meade's brigade and two regiments from Morell's division.

The 1st North Carolina suffered 50% casualties (133 men killed, wounded, or captured) and also lost its commander, Col. Montford Stokes.

This was a strategic decision of grave import because it meant that, without the railroad to supply his army, he had to abandon his siege of Richmond.

[13] Overall, the battle was a Union victory "by any definition",[1] in which the Confederates suffered heavy casualties and achieved none of their specific objectives due to the seriously flawed execution of Lee's plan.

[15] Company F of the 8th Pennsylvania Reserve Regiment (also referred to as The Hopewell Rifles) from Bedford County, PA was not informed of the orders to retreat after being sent ahead to skirmish.