McClellan's troubles began the moment his men stepped off the transports. On April 5, 1862, the IV Corps under Brigadier General Erasmus D. Keyes made contact with Confederate defenses at Lee's Mill, an area McClellan expected to walk through unopposed. Instead, they found the Warwick Line - a chain of redoubts, rifle pits, and fortifications behind the Warwick River, stretching from Yorktown to Mulberry Island. The man behind these defenses, Brigadier General John B. Magruder, was a born showman. He marched a single company in circles through a clearing to create the illusion of endless reinforcements arriving. He spread his artillery far apart, firing sporadically to suggest strength across the entire front. Union scouts reported an army of 100,000 in their path. In reality, Magruder commanded just 11,000 men. McClellan, believing himself outnumbered, halted his advance and ordered siege operations at Yorktown - giving the Confederates weeks to bring up reinforcements. By mid-April, Magruder had 35,000 men, barely enough to hold his line but far more than he started with.

When the Confederates finally withdrew from Yorktown under General Joseph E. Johnston, McClellan's pursuit stumbled into the first pitched battle of the campaign on May 5 at Williamsburg. Nearly 41,000 Union soldiers engaged 32,000 Confederates around Fort Magruder, a large earthen fortification straddling the road from Yorktown. Joseph Hooker's division assaulted the fort and its outlying rifle pits, was repulsed, and then faced Confederate counterattacks directed by James Longstreet that threatened to overwhelm his isolated force. Hooker had expected reinforcements from Baldy Smith's division to arrive when they heard the fighting, but Smith had been halted by his superior, Edwin Sumner, more than a mile away. On the opposite flank, Winfield Scott Hancock seized a position and beat back a disorganized Confederate attack - fewer than 1,200 men charging 3,400 with no artillery support. McClellan's description of Hancock's 'superb' performance earned him a nickname that lasted a lifetime. Confederate casualties were 1,682, Union 2,283. McClellan called it a 'brilliant victory.' In truth, the battle had merely allowed Johnston to continue his retreat toward Richmond.

By late May, McClellan's army straddled the Chickahominy River outside Richmond, one-third south of the river and two-thirds north - a dangerous position that Johnston resolved to exploit. On May 31, Johnston threw 51,000 men against the 33,000 Union troops isolated south of the swollen river. The plan was complex and it fell apart immediately. Longstreet either misunderstood or deliberately modified his orders, sending his divisions down the wrong road and delaying the assault by five hours. When D.H. Hill finally attacked at 1 p.m. out of sheer impatience, his brigades hit the inexperienced division of Silas Casey, which buckled but fought fiercely. The battle seesawed until Edwin Sumner, hearing the guns from north of the river, sent John Sedgwick's division across the treacherous Grapevine Bridge on his own initiative. The weight of the crossing troops held the collapsing span steady against the rushing current; after the last man crossed, the bridge was swept away. At dusk, Johnston himself was wounded by an artillery fragment and evacuated to Richmond. The next day, Jefferson Davis replaced the army's temporary commander with Robert E. Lee - a decision that would transform the war.

Lee used the month-long pause after Seven Pines to fortify Richmond's defenses and prepare an offensive. He also sent J.E.B. Stuart's cavalry on an audacious ride completely around McClellan's army from June 13 to 15 - militarily pointless but psychologically devastating to the Union commander, who was already paralyzed by faulty intelligence suggesting the Confederates outnumbered him. Then Lee struck. From June 25 to July 1, the Seven Days Battles raged east of Richmond in a series of fierce engagements. None were significant Confederate tactical victories - the Battle of Malvern Hill on the final day was a devastating Confederate defeat, with wave after wave of infantry shattered by massed Union artillery. But the sheer tenacity of Lee's attacks, combined with the sudden appearance of Stonewall Jackson's 'foot cavalry' on his western flank, broke McClellan's nerve. He pulled his army back to a base on the James River at Harrison's Landing. The campaign that was supposed to end the war in weeks had failed. Lincoln ordered the army back to Washington to support John Pope's army, and the Virginia Peninsula fell quiet.

The Virginia Peninsula remains etched with the campaign's footprint. Fort Monroe, where McClellan's armada landed, still stands at the tip of the Peninsula at Old Point Comfort - one of the few Union-held positions in Virginia throughout the entire war. The earthworks at Yorktown and Williamsburg have largely returned to forest, but Fort Magruder's site is marked in the city of Williamsburg. Drewry's Bluff, where Confederate guns turned back a Union naval squadron on May 15 and saved Richmond from a river assault, overlooks a sharp bend in the James River. The Chickahominy River, which flooded catastrophically during the campaign and split McClellan's army in two, still meanders through swampy bottomland east of Richmond. The Peninsula campaign produced over 36,000 casualties on both sides and introduced Robert E. Lee as the commander who would lead the Confederacy for the rest of the war. McClellan, the Young Napoleon who once told Lincoln 'I can do it all,' never held independent command in a major campaign again.