 Despite the strength of Malvern Hill , as demonstrated in the battle , McClellan felt he needed to continue with his planned withdrawal to Harrison 's Landing , to Fitz John Porter 's chagrin . Porter felt that the Army of the Potomac should remain atop the hill or perhaps even continue their advance to Richmond . McClellan however insisted that Confederate troops greatly outnumbered his own , felt he could not protect Harrison 's Landing from his current position at Malvern Hill , and feared being cut off from his supply depot . McClellan 's mentality prevailed . The Union batteries and McClellan 's engineers began moving to Harrison 's Landing soon after the end of the Battle of Malvern Hill . Starting at about 11 p.m. unit after unit began to follow . Within hours , nearly all of McClellan 's Army of the Potomac was marching towards Harrison 's Landing . Once the last of these men had crossed the Turkey Island Bridge , they destroyed the bridge and felled trees over it to stymie any pursuit , leaving the James River between the Union and Confederate armies . 
