As part of the Peninsula campaign, Confederate forces strike Union troops at the Battle of Seven Pines (Fair Oaks) in Virginia. During May 1862, the Army of the Potomac, under the command of George B. McClellan, slowly advanced up the James Peninsula after sailing down the Chesapeake Bay by boat. Confederate commander Joseph Johnston had been cautiously backing his troops up the peninsula in the face of the larger Union force, giving ground until he was in the Richmond perimeter. When the Rebels had backed up to the capital, Johnston sought an opportunity to attack McClellan and halt his advance.
That chance came when McClellan's forces were straddling the Chickahominy River. The swampy ground around the river was difficult to maneuver, and the river was now a raging torrent from the spring rains. A major storm on May 31 threatened to cut the only bridge links between the two wings of the Union army.
Johnston attacked one of McClellan's corps south of the river on May 31 in a promising assault. The plan called for three divisions to hammer the Federal corps from three sides, but the inexperienced Confederates were delayed and confused. By the time the attack came, McClellan had time to muster reinforcements and drive the Rebels back. A Confederate attack the next day also produced no tangible results. The Yankees lost 5,000 casualties to the Rebels' 6,000.
But the battle had two important consequences. McClellan was horrified by the sight of his dead and wounded soldiers, and became much more cautious and timid in battle, actions that would eventually doom the campaign. And since Johnston was wounded during the battle's first day, Robert E. Lee replaced him. Lee had been serving as Confederate President Jefferson Davis' military advisor since his undistinguished service in western Virginia during the war's first year. The history of the war in the eastern theater drastically changed as Lee ascended the ranks. His leadership and exploits soon became legend.