Battle of Gaines's Mill - Aftermath

Aftermath

Gaines's Mill was an intense battle, the largest of the Seven Days and the only clear-cut Confederate tactical victory of the Peninsula Campaign. Union casualties from the 34,214 engaged were 6,837 (894 killed, 3,107 wounded, and 2,836 captured or missing). Of the 57,018 Confederates engaged, losses totaled 7,993 (1,483 killed, 6,402 wounded, 108 missing or captured). Since the Confederate assault was conducted against only a small portion of the Union Army (the V Corps, one fifth of the army), the army emerged from the battle in relatively good shape overall. Lee's victory, his first of the war, could have been more complete if it were not for the mishaps of Stonewall Jackson. Historian Stephen W. Sears speculates that it were not for Jackson's misdirected march and his poor staff work, the major assault that Lee unleashed at 7 p.m. could have occurred three or four hours earlier. This would have put Porter in grave jeopardy, without any last-minute reinforcements and the cover of darkness. He quotes Edward Porter Alexander, prominent Confederate artillery officer and postwar historian: "Had Jackson attacked when he first arrived, or during A.P. Hill's attack, we would have had an easy victory—comparatively, & would have captured most of Porter's command."

Although McClellan had already planned to shift his supply base to the James River, his defeat unnerved him and he precipitously decided to abandon his advance on Richmond and begin the retreat of his entire army to the James. Gaines's Mill and the Union retreat across the Chickahominy was a psychological victory for the Confederacy, signaling that Richmond was out of danger.