The Peninsula Campaign
Arriving on the Peninsula with 121,500 men, McClellan slowly began his advance towards Richmond. Upon reaching Yorktown, he found that the Confederates had built a fortified line from the York River in the north to the James River in the south. Tricked by Confederate General John Magruder into believing the line was heavily manned, McClellan paused and ordered heavy siege guns to be brought up from his base at Fortress Monroe. After taking a month to prepare his assault, McClellan learned that the Confederates had fallen back to Williamsburg. The Union army pursued them and won a minor victory outside the colonial town on May 5.
Continuing the march towards Richmond, McClellan's army became divided by the Chickahominy River. Seeing an opportunity to isolate part of the larger Union force, Johnston moved forward to attack on May 31. Striking near Seven Pines (Fair Oaks), the battle was tactically inconclusive but did see Johnston badly wounded. He was replaced by the more active General Robert E. Lee. In addition, the fight caused McClellan to pause again and wait for further reinforcements.
The Seven Days' Battles
While McClellan remained inactive for three weeks, Lee worked frantically to improve Richmond's defenses. On June 25, he began a series of battles designed to push McClellan away from the city. Striking first at Mechanicsville on June 26, and again at Gaine's Mill the next day, Lee seized the initiative and put the cautious McClellan on the defensive. Believing Lee to significantly outnumber him, McClellan began to fall back towards his base at Harrison's Landing on the James River. In the process his troops were defeated at Frayser's Farm on the 30th, and required heavy artillery support to stop Lee at Malvern Hill on July 1. Blaming Lincoln's unwillingness to send more troops for his defeat, McClellan and the Army of the Potomac were effectively cornered at Harrison's Landing.The Second Battle of Manassas
While McClellan was retreating on the Peninsula, the Union troops around Washington were reorganized into the Army of Virginia with Major General John Pope in command. Charged with protecting Washington and advancing on Richmond from the north, Pope moved towards Gordonsville, but found that Confederate troops under Jackson had arrived there first. Lee, no longer feeling that the timid McClellan was a threat and seeing that the Union army was evacuating the Peninsula, began shifting his men north hoping to destroy Pope.
Assuming a position along the Rappahannock River, Pope was soon forced to retreat toward Manassas after Jackson's troops and Confederate cavalry under General J.E.B. Stuart marched around his flank. While Pope retreated towards Centreville, Jackson took a defensive position behind an unfinished railroad cut on the old Bull Run battlefield. On August 28, Jackson attacked Pope, hoping to hold him until the rest of Lee's army could arrive. Over the next two days the sides exchanged punches until a flanking movement by General James Longstreet drove the Union troops from the field.
Antietam and Emancipation
In September, 1862, Lee decided to attempt an invasion of the North with the goal of cutting the rail lines to Washington and securing supplies for his army. To counter this move, Lincoln recalled McClellan and gave him command of all Union forces in the area. While marching north, Lee divided his 45,000-man army sending Jackson to capture Harper's Ferry and Longstreet to occupy Hagerstown, MD. McClellan slowly pursued with 87,000 men and arrived at Frederick, MD on the 13th. While there a copy of Lee's operations orders were found by Union soldiers. Despite knowing that Lee's army was separated, McClellan waited over eighteen hours before moving west to engage the enemy. On the 14th, McClellan's men forced their way through the mountain passes causing Lee to order his army to concentrate at Sharpsburg, MD.
On the morning of the 17th, McClellan began assaulting Lee's lines around Sharpsburg and Antietam Creek. The Union attacks through the day lacked coordination, allowing Lee to shift his outnumbered men along the line to meet each threat. In addition, McClellan, believing that Lee's force was superior, refused to commit his reserves to exploit Union successes. When the fighting ended late in the day, McClellan had lost a golden opportunity to crush Lee. That night the Confederates withdrew across the Potomac to the Shenandoah Valley. The Battle of Antietam was the single bloodiest day in American history with the two sides suffering over 23,000 casualties. In the wake of McClellan's victory, Lincoln issued the Emancipation Proclamation which freed the slaves in Confederate-held territory. This document signaled a major shift in Union war aims from fighting to preserve the nation to fighting to free the slaves.
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