Prelude to the Peninsula Campaign
Within twenty-four hours of the Union’s defeat at the First Battle of Bull Run on July 21, 1861, the Lincoln administration called upon George B. McClellan to lead the Union war effort. McClellan spent the first few months of his command fortifying Washington, DC, and reorganizing federal forces. The Northern public and politicians, however, wanted action. Accordingly, McClellan devised plans for an offensive to capture the Confederate capital at Richmond, Virginia, and bring a quick conclusion to the war. McClellan incorrectly believed that the main Confederate army, entrenched near Manassas Junction, outnumbered the Union Army of the Potomac. Eschewing a major battle, he planned to use the Union’s superior naval resources to transport his army down the Chesapeake Bay, outflanking the Confederates and capturing Richmond.
Army of the Potomac on the Move
The offensive began on March 17, when McClellan began transporting his army of approximately 120,000 men to Fort Monroe, on the peninsula between the York and James Rivers in southeastern Virginia. On April 4, the Army of the Potomac began its advance up the peninsula toward Yorktown. The next day, the advance came to a halt when the Federals encountered Confederate forces of about 10,000, dug in along the Warwick River. Once again, erroneously believing that the Confederates outnumbered his army, McClellan settled in for a siege rather than an attack. The Siege of Yorktown resulted in a one-month delay that enabled Confederate General Joseph Johnston to redeploy troops from northern Virginia to the peninsula.
Battle of Williamsburg
On May 4, McClellan finally launched an assault on Yorktown, only to find that the Confederate defenders were moving back toward Richmond. McClellan sent his army in pursuit of the retreating Confederates, and on May 5, the first major encounter of the Peninsula Campaign occurred near Williamsburg. The results of the Battle of Williamsburg, also known as the Battle of Fort Magruder, were inconclusive, but the rearguard of Confederate General James Longstreet held off the Union attack long enough to enable Johnston’s main army to establish new defensive lines protecting Richmond.
Once again, McClellan’s offensive stalled as he awaited reinforcements and devised his plans for capturing Richmond. As McClellan lingered at the gates of Richmond, General Thomas “Stonewall” Jackson inflicted a series of defeats on Union forces in the Shenandoah Valley. President Lincoln, perceiving Jackson’s actions as a threat to Washington, recalled the reinforcements McClellan expected on the peninsula.
Robert E. Lee Replaces Joseph E. Johnston
Meanwhile, McClellan had encamped his army on both sides of the Chickahominy River, east of Richmond. When heavy spring rains flooded the Chickahominy, Johnston seized the opportunity to attack McClellan’s army, divided by the swollen river. The Federals repelled the Confederate attack at the Battle of Seven Pines, also known as the Battle of Fair Oaks (May 31 to June 1, 1862), but McClellan lost his initiative. During the battle, an exploding Union shell severely injured Johnston. Confederate President Jefferson Davis soon named Robert E. Lee to replace Johnston.
Seven Days Battles
Following the Battle of Seven Pines, McClellan redeployed most of his army south of the Chickahominy River and continued to plan for a siege of Richmond. Taking advantage of McClellan’s inactivity, on June 25, Lee launched the first of six assaults on Federal troops in seven days, collectively known as the Seven Days Battles (June 25 to July 1, 1862). Although the Battle of Gaines Mills was the only engagement in the series that produced a tactical Confederate victory, the battles achieved Lee’s strategic aim of driving McClellan away from Richmond. The Army of the Potomac retreated down the peninsula until President Lincoln and General-of-Army Henry Halleck recalled it on August 3, to support the Army of Virginia at the Second Battle of Bull Run (August 28 to 30, 1862).
The Outcome of the Peninsula Campaign
The failure of the Peninsula Campaign was a critical turning point in the war. In May, the Army of the Potomac was only six miles from the Confederate capital. By July, with McClellan’s army in retreat, Lee could turn his attention to the Union Army of Virginia, less than thirty miles from Washington, and inflict another disastrous Federal defeat at the Second Battle of Bull Run, opening the way for a Confederate invasion of the North.