The Battle of Fair Oaks, or Seven Pines, was the first Confederate attempt to dislodge General George B. McClellan's Army of the Potomac from their position just outside Richmond. McClellan's Peninsula campaign had seen the Union army slowly close on the Confederate capitol, finally reaching within a few miles of the city in May 1862.
McClellan's army was awkwardly placed on both sides of the Chickahominy Creek. The right flank of his army was north of the river, protecting its supply lines and the route that any reinforcements from Washington would take. The left flank was south of the river, threatening Richmond. The danger was that the Chickahominy was prone to sudden rises in water level, which had the potential to wipe away the temporary pontoon bridges built by McClellan's engineers.
The left flank of McClellan's army was the weaker of the two. It contained two of his five army corps - Heintzelman's Third Corps and Keyes's Fourth Corps, both 17,000 strong. Next in line, on the other side of the Chickahominy, was Sumner's Second Corps, of roughly the same size. Roughly 34,000 of McClellan's nearly 100,000 men were available to resist any Confederate attack south of the river.
The Confederate commander at Richmond, General Joseph Johnston, now had just over 60,000 men at his disposal. In theory he had more than enough men to inflict a significant defeat on McClellan's isolated left wing, but in the battle that was to develop around Fair Oaks and Seven Pines neither side managed to get more than a fraction of their available men into action.
Johnston's original plan was for an attack on the stronger Federal right wing. This was because he had learnt that another 40,000 Federal troops under General McDowell were about to join McClellan. This move was cancelled after Stonewall Jackson's first victories in the Shenandoah Valley. Johnston now decided to attack south of the Chickahominy instead.
His new plan involved an early morning attack by four divisions on 31 May. They would begin their march at daybreak (roughly 4 a.m.), and fall on Keyes' corps before 8 a.m. Keyes's corps was closest to Richmond. Most of the corps was on the Williamsburg road, with a smaller force a little further north at Fair Oaks. Heintzelman's corps was further east. Sumner's corps was slightly closer, but on the other side of the Chickahominy, which was now in flood. Keyes's corps was poorly entrenched and dangerously isolated.
The Confederate plan quickly went wrong. Longstreet had been meant to attack Keyes's vulnerable right flank, while D.H. Hill attacked his main lines on the Williamsburg Road. Instead, Longstreet mistakenly moved his men onto the Williamsburg Road, causing a lengthy delay in the start of the attack. The entire plan was badly handled. Significant orders were only dispatched on the day itself, causing inevitable delays. The result of all this was that the attack was finally launched at 1 p.m., hours after it should have started.
The right wing of the Confederate attack met with immediate success, pushing Keyes's men out of their first line of defence and back to their second line at Seven Pines. The left wing looked to be gaining a similar level of success against the small Federal force at Fair Oaks, but at 2.30 p.m. General Sumner had begun to move his troops across the Chickahominy, using bridges that were partly underwater! The Confederate left wing made repeated efforts to dislodge this new force, but without success. As darkness fell across the battlefield, the Confederate attack had ground to a halt. Federal reinforcements were constantly reaching the battlefield. Johnston himself was badly wounded late in the day.
The next day saw Robert E. Lee promoted to command the Confederate armies around Richmond. His first job was to deal with a Federal counterattack that soon recaptured all of the ground lost on the first day of the battle. Lee's response was to call off any further fighting, and pull his army back into the defences of Richmond, where he began to prepare for his own counterattack. That attack would be launched at the end of June, and resulted in the Seven Days's Battles. McClellan declared himself pleased with the change of Confederate commander, an opinion he would later be forced to reconsider.See also: The Armies at the battle of Seven Pines or Fair Oaks