Following the Confederate withdrawal from their Yorktown position, Maj. Gen. George B. McClellan was not prepared to mount an immediate pursuit with his entire force from the siege lines he had occupied for nearly a month. Initially, he was able to send forward only a portion of his army, led by the Third Corps of Samuel P. Heitzelman, to follow Gen. Joseph E. Johnston's Confederates. Heitzelman's divisions, led by Brig. Gens. Joseph Hooker and Phil Kearny, made contact with Johnston's army four miles southeast of Williamsburg. Hooker assaulted Fort Magruder, an earthen fortification alongside the Williamsburg Road, but was repulsed. Confederate counterattacks, directed by Lieut. Gen. James Longstreet, threatened to overwhelm Hooker's men until Kearny’s division arrived to stabilize the Federal left. A brigade of Brig. Gen. Darius N. Couch's Fourth Corps arrived to support Hooker's right. Brig. Gen. Winfield S. Hancock’s brigade moved to threaten the Confederate left flank, occupying two abandoned redoubts. The Confederates counterattacked Hancock unsuccessfully, but his localized success was not exploited. Johnston continued his withdrawal up the peninsula that evening. McClellan miscategorized the battle as a "brilliant victory" over superior forces, but neither commander had committed his entire army to the fight. The battle was, however, the largest engagement of the Peninsula Campaign until Seven Pines three weeks later.