The Peninsula Campaign was the strategic concept of Union Army Commander–in–Chief Major General George B. McClellan. By advancing up the Peninsula, McClellan would avoid suffering the high casualties caused by a march south on Richmond from northern Virginia. The powerful Union navy could first transport McClellan’s army to the Peninsula, then, using the James and York rivers, protect that army’s flanks as it advanced toward Richmond. It was an excellent plan and McClellan’s army seemed unstoppable. Yet, despite all these advantages, he failed to achieve his goals.

Major General Benjamin Franklin Butler was the first Union commander to recognize the strategic importance of the Virginia Peninsula. His defeat during the June 10, 1861, Battle of Big Bethel ended Butler’s feeble effort to capture Richmond via the Peninsula. McClellan, however, viewed the Peninsula as his second choice. His initial plan was an advance against Richmond by way of Urbanna on the Rappahannock River. This would have placed the Union army behind General Joseph E. Johnston’s Confederate army then positioned in northern Virginia. When Johnston withdrew further south from the Manassas Line on March 8, 1862, McClellan had to scrap his original plan and select his second alternative, the Peninsula. McClellan believed that by using Fort Monroe as a base, he could march against Richmond "with security, altho’ with less celebrity and brilliancy of results, up the Peninsula."

In early March 1862, McClellan found himself under considerable political pressure to launch some advance against Richmond. Even as he shared the merits of his plan with President Abraham Lincoln, it started to unhinge. The emergence of the ironclad ram CSS Virginia (the captured and refitted USS Merrimack) on March 8, 1862, sent shock waves through the Union command. In one day, the Virginia destroyed two Union warships, the USS Congress and USS Cumberland, threatening Federal control of Hampton Roads. A strategic balance was quickly gained when the novel Union ironclad USS Monitor arrived and fought the Virginia to a standstill the next day. While both sides claimed victory, the Virginia’s presence denied the James River to Federal use.

Confident that the Monitor could hold off any advance against his transports by the Confederate ironclad, McClellan proceeded with his campaign. He began shipping his 121,500–strong army with all of its supplies and armaments to Fort Monroe on March 17, 1862, intending to move against Richmond by way of the York River.
  

On April 4, 1862, McClellan’s army began its march up the Peninsula. The next day the Army of the Potomac found its path to Richmond slowed at first by heavy rains and then blocked by Confederate Major General John Bankhead Magruder’s 13,000–strong "Army of the Peninsula." Since his June 1861 victory at Big Bethel, Magruder had constructed three defensive lines across the Peninsula. The most formidable of these lines was the second, a line which stretched from Yorktown, along the Warwick River, to the James River. As McClellan carefully surveyed the extensive Confederate fortifications, "Prince John" Magruder paraded his troops along the earthworks, deluding the Union commander into believing he was outnumbered.

The events of April 5 changed McClellan’s campaign. Not only were his plans for a rapid movement past Yorktown upset by the unexpected Confederate defenses along the Warwick River, but also by Lincoln’s decision not to release General Irwin McDowell’s I Corps from northern Virginia to use in a flanking movement against the Confederate batteries at Gloucester Point. The U. S. Navy, too, refused to attempt any offensive action in the York River. Flag Officer Louis Goldsborough feared that the CSS Virginia might attack the Union fleet while it attempted to silence the Confederate guns at Yorktown and Gloucester Point. Since McClellan’s reconnaissance, provided by detective Alan Pinkerton and Professor Thaddeus Lowe’s balloons, confirmed his belief that he was outnumbered by the Confederates, the Union commander thought that he had no choice but to besiege the Confederate defenses.

As his men built gun emplacements for the 103 siege guns McClellan had brought to the Peninsula, General Joseph E. Johnston moved his entire Confederate army down to the lower Peninsula from his camps in northern Virginia. Johnston believed that the Confederate position was weak, noting that, "No one but McClellan could have hesitated to attack." McClellan’s men did make one attempt to break the Confederate Warwick–Yorktown Line. Brigadier General William F. "Baldy" Smith sent elements of the Vermont Brigade across the Warwick River to disrupt Confederate control of Dam No. 1. The poorly coordinated assaults on April 16, 1862, failed to break through the vulnerable Confederate target.

The siege continued another two weeks even though Johnston counselled retreat. Johnston advised that "the fight for Yorktown must be one of artillery, in which we cannot win." Finally, just as McClellan made his last preparations to unleash his heavy bombardment on the Confederate lines, Johnston abandoned the Warwick– Yorktown Line on May 3.

McClellan was surprised by the Confederate withdrawal. The Union commander attempted to cut off Johnston’s retreat, ordering Brigadier General Edwin V. "Bull" Sumner to attack the Confederate rear guard. The result was the bloody, indecisive May 5 Battle of Williamsburg. Fighting raged in front of Fort Magruder until dark, but it was Brigadier General Winfield Scott Hancock’s flanking move into several unmanned redoubts on the Confederate left which forced the Southerners to abandon the Williamsburg Line.

McClellan did not arrive on the battlefield until dark, as the engagement was ending. He had been in Yorktown, supervising the embarkation of Brigadier General William B. Franklin’s division onto transports. Franklin rushed up the York River to block Johnston’s withdrawal to Richmond. Although able to secure a beachhead at Eltham’s Landing on May 6, Franklin moved inland timidly. There Franklin was blocked by John Bell Hood’s Texans and Johnston made his escape.

President Lincoln, concerned by what he deemed McClellan’s general lack of initiative, arrived at Fort Monroe on May 6. Two days later, the President supervised the Union’s unsuccessful naval attack against Norfolk. Across the Elizabeth River from Norfolk was Portsmouth’s Gosport Navy Yard. Gosport was the largest naval base and shipyard in the Confederacy and served as the Virginia’s home port. The Confederate retreat from the lower Peninsula had forced Major General Benjamin Huger to abandon Norfolk on May 9. Without its base and unable to steam up the James River to Richmond because of its deep draught, the Virginia was destroyed by its crew on May 11, 1862. The door to the Confederate capital via the James River now lay open. A Union fleet, moved up the river and approached within seven miles of Richmond. On May 15, 1862, Confederate batteries atop Drewry’s Bluff repulsed the Federal advance.

As McClellan’s army neared the outskirts of the Confederate capital by the end of May, he extended his right to meet expected reinforcements from Northern Virginia. In the meantime, "Stonewall" Jackson’s successful operations in the Shenandoah Valley prompted Lincoln to continue to hold these reinforcements around Fredericksburg to help protect Washington from any Confederate advance. McClellan now found his army divided by the swampy Chickahominy River.

Confederate commander Joe Johnston was under pressure from Confederate President Jefferson Davis to do something about the approaching Federals. Taking advantage of heavy rains which had made the Chickahominy nearly impassable, Johnston attacked McClellan’s army south of the river around the villages of Seven Pines and Fair Oaks. The poorly coordinated assaults on May 31 failed and Johnston was seriously wounded. The next day, June 1, 1862, the battle continued, but Robert E. Lee, who assumed command of the Confederate forces around Richmond, ordered a withdrawal that afternoon.

Lee, formerly Jefferson Davis’ Military Advisor, now readied the Confederate army for an offensive strike against McClellan. In preparation for his attack against the Union army, Lee ordered Brigadier General J. E. B. Stuart to reconnoiter the Army of the Potomac’s right flank. Stuart discovered that the Union flank was exposed, but he exceeded his instructions and rode completely around the Federal army. It was a spectacular maneuver which, unfortunately for the Confederates, alerted McClellan to his weak position, thereby facilitating McClellan’s eventual change of base to Harrison’s Landing on the James River.

Lee’s offensive, called the Seven Days’ Battles, began on June 25, 1862, when elements of the Union army advanced against Lee’s Confederates south of the Chickahominy. Lee, after ordering Jackson’s Valley command to Richmond, unleashed his combined forces against an exposed Union corps above the Chickahominy near Mechanicsville. The June 26 attack, called the Battle of Beaver Dam Creek, began a series of engagements which forced McClellan to retreat across the Peninsula to the James River. The Seven Days’ Battles ended on July 1, 1862, when the Union army repulsed several bloody and uncoordinated Confederate assaults at Malvern Hill. McClellan’s army reached safety at Harrison’s Landing, but Lee’s offensive, although costly in men, achieved its objective –– Richmond was saved.

Despite all his advantages, McClellan’s Peninsula Campaign ended in failure. Richmond’s redemption provided hope for the young Confederacy, particularly after a series of recent defeats in the West. In the Spring of 1862, McClellan had a tremendous opportunity. If he had pressed on Richmond and captured the Confederate capital, McClellan might have won the war and our history might well have taken a very different course. Instead, the Civil War lasted for three more bloody years.