The Confederate victory at the Battle of Gaines' Mill on June 27, 1862, featured the largest single assault of the American Civil War and prompted Major General George B. McClellan to suspend his plans to invest Richmond during the Peninsula Campaign.
Prelude to the Battle
On March 17, 1862, Union General George B. McClellan launched his Peninsula Campaign. After transporting the Army of the Potomac by ships to the Virginia peninsula between the York and James Rivers, McClellan planned to advance on Richmond and bring the American Civil War to a quick conclusion. By late May, the Federals had fought their way to the outskirts of the Confederate capital.
Battle of Seven Pines
On May 31, Confederate General Joseph E. Johnston struck back at the Battle of Seven Pines. Two days of hard fighting rendered a tactical draw and high casualties on both sides. The aftermath of the engagement, however, produced two important strategic developments. First, Robert E. Lee assumed command of the Army of Northern Virginia after Johnston suffered a severe wound during the fighting. Second, the high casualty rate convinced McClellan to invest Richmond rather than to risk costly assaults against the Rebel defenses around the capital.
Reprieve for Lee
For nearly a month, McClellan sat idly, developing plans for a siege. The unexpected reprieve presented Lee with an opportunity to organize his command and to plan an offensive designed to drive the Union army away from Richmond. Toward the end of June, McClellan developed a renewed sense of urgency when he learned that Major General Stonewall Jackson was moving to reinforce Lee after concluding his highly successful Shenandoah Valley Campaign.
Battle of Oak Grove
On June 25, at the Battle of Oak Grove, Rebel forces repulsed McClellan’s attempt to advance his siege artillery approximately one and one-half miles closer to the capital so he could “shell the city and take it by assault.”
Battle of Beaver Dam Creek
On the next day, Lee seized the initiative. Leaving only two divisions to protect Richmond from the bulk of McClellan’s army (four corps positioned south of the Chickahominy River), Lee attacked Brigadier General Fitz John Porter’s 5th Corps, which was isolated north of the river. Lee’s plan was to defeat Porter’s corps, which formed the right (northern) wing of the Federal army, and then to sever McClellan’s supply line, the York and Richmond Railroad.
Events did not unfold as Lee had planned, and the Northerners rebuffed the Confederates at the Battle of Beaver Dam Creek. Nonetheless, the specter of Jackson on his right flank prompted McClellan to move his supply center to the James River, handing Lee what the Southerner failed to achieve on the battlefield. Despite the Federal victory, McClellan ordered Porter to abandon his entrenchments at Beaver Dam Creek during the night and to fall back to higher ground as the arduous task of shifting the Union supply center began.
Federals Deploy Near Gaines’ Mill
During the night of June 26–27, Porter deployed his troops in an arc 1.5 miles long southeast of a mill owned by Dr. William F. Gaines. Porter’s new line on high ground behind Boatswain’s Creek, with the Chickahominy River to his back, was protected by a thick growth and offered an excellent field of fire for repelling enemy assaults.
Lee Moves Against Porter
Still hoping to crush Porter’s army before it could cross the Chickahominy, Lee continued his assault on June 27. His plan was similar to the one that failed the day before, sending two divisions commanded by A. P. Hill and James Longstreet against the Yankee center, while Stonewall Jackson and D.H. Hill tried to flank Porter on the right and then to hit the Northerner from the rear.
Costly Confederate Attack
The action got underway early in the morning when A. P. Hill’s division moved across Beaver Dam Creek with little resistance. Expecting to be pursuing an army in retreat, Hill instead encountered Porter’s stout new line. Jackson, meanwhile, had taken a wrong turn and for the second time in two days was late to the battlefield. Like the day before, Hill waited until 2:30 and then launched a futile attack against the Yankee center that lasted two hours and produced two thousand casualties.
At approximately 3:30 p.m. Major General Richard Ewell’s division was the first of Jackson’s command to approach the Union lines. Lee ordered Ewell to attack immediately, before his entire division arrived. Lee also ordered D.H. Hill and Longstreet to join in what became a series of disjointed assaults. By 4:30, Jackson’s full division arrived, but communication problems delayed its deployment.
Federal Line Crumbles
By sunset, Lee finally had all of his generals in place. At 7 p.m. he ordered a massive charge covering a two-mile front. Over 32,000 Rebel soldiers stormed the Bluecoats in the largest single assault of the war. Porter’s men held on gamely, but following some of the more brutal fighting of the Civil War, Brigadier-General John Bell Hood’s Texas Brigade broke through on Longstreet’s front. The Federal line then began to crumble, and the Yankees began to fall back toward the Chickahominy River. As the Rebels pursued, Union Brigadier General Philip St. George Cooke, the father-in-law of Confederate General J. E. B. Stuart, ordered a foolhardy cavalry charge that sacrificed nearly an entire Federal regiment and achieved nothing.
Saved by Darkness
Although Porter’s line broke, the onset of darkness saved his corps from total destruction. Confederates took many of Porter’s spent and dazed men prisoner, but the Union general got much of his command across the Chickahominy River during the night. At roughly 4 a.m. on June 28, Porter burned the bridges spanning the river, leaving Lee’s pursuers on the opposite side.
Aftermath of the Battle
Although Lee failed to destroy Porter’s corps as he had hoped, the Battle of Gaines’ Mill was a significant tactical, strategic, and psychological victory for the Confederacy. Although the Rebels suffered more causalities (7,993 men, including 1,483 killed, 6,402, wounded, 108 missing or captured), compared with Union losses (6,837 soldiers, including 894 killed, 3,107 wounded, 2,836 missing or captured), Lee won the field and forced Porter to retreat across the Chickahominy.
More importantly, the Confederate victory caused McClellan to lose his nerve and suspend his plans to invest Richmond. Although he refused to refer to it as a retreat, McClellan ordered the four corps that he had poised at the doors of the Confederate capital to withdraw south. By the end of the week, Richmond was no longer in danger, and new life had been breathed into Confederate hopes.