text: Lee's intricate plan went awry immediately. Jackson's men, fatigued from their recent campaign and lengthy march, ran at least four hours behind schedule. By 3 p.m., A.P. Hill grew impatient and began his attack without orders, a frontal assault with 11,000 men. Porter extended and strengthened his right flank and fell back to concentrate along Beaver Dam Creek and Ellerson's Mill. There, 14,000 well entrenched soldiers, aided by 32 guns in six batteries, repulsed repeated Confederate attacks with substantial casualties.
  Jackson and his command arrived late in the afternoon and he ordered his troops to bivouac for the evening while a major battle was raging within earshot. His proximity to Porter's flank caused McClellan to order Porter to withdraw after dark behind Boatswain's Swamp,  to the east. McClellan was concerned that the Confederate buildup on his right flank threatened his supply line, the Richmond and York River Railroad north of the Chickahominy, and he decided to shift his base of supply to the James River. He also believed that the diversions by Huger and Magruder south of the river meant that he was seriously outnumbered. (He reported to Washington that he faced 200,000 Confederates, but there were actually 85,000.) This was a strategic decision of grave importance because it meant that, without the railroad to supply his army, he would be forced to abandon his siege of Richmond. A.P. Hill, now with Longstreet and D.H. Hill behind him, continued his attack, despite orders from Lee to hold his ground. His assault was beaten back with heavy casualties.