PENINSULAR CAMPAIGN (1862), an advance against Richmond, began on 4 April 1862, when Maj. Gen. George B. McClellan departed from Fortress Monroe with his Union army of approximately 100,000 to attack the Confederate capital by way of the peninsula formed by the York and James Rivers. McClellan had counted on a larger force and aid from the navy on the James River. The administration withheld 45,000 troops to protect Washington, D.C., and the navy was unable to help because of the menace of the Merrimack and Confederate shore batteries.
The campaign unfolded in three phases. The early Union advance was marked by Confederate resistance behind entrenchments across the peninsula from Yorktown. On 5 April McClellan besieged Yorktown, which was evacuated on 3 May. He then pushed slowly forward, fighting at Williamsburg on 5 May, reaching and straddling the Chickahominy River on 20 May and facing a strengthened Confederate force under Gen. Joseph E. Johnston.
Help expected from Union Gen. Irvin McDowell's 40,000 men was lost to McClellan in May when Confederate Gen. T. J. ("Stonewall") Jackson's Shenandoah Valley campaign scattered or immobilized the Union armies before Washington. The first phase of the campaign ended with the indecisive two-day Battle of Fair Oaks (or Battle of Seven Pines), 31 May and 1 June. Johnston was wounded on 1 June and Robert E. Lee succeeded to his command.
After Fair Oaks came the second phase, three weeks without fighting, marked by Confederate Gen. J. E. B. Stuart's spectacular cavalry raid around the Union army, from 11 to 13 June.
McClellan, reinforced, intended to retake the offensive, but Lee forestalled him and opened the third phase of the campaign by attacking the Union right at Mechanicsville on 26 June. This began the Seven Days' Battles, during which McClellan changed his base to the James River, fending off waves of Confederate attacks as the Union Army retreated to its base at Harrison's Landing. With the appointment on 11 July of Gen. Henry W. Halleck to command all land forces of the United States, the Army of the Potomac began its withdrawal from the peninsula.
Union casualties in the campaign were approximately 15,000, with 1,700 killed; Confederate losses were about 20,000, with 3,400 killed. The Union forces greatly outnumbered the Confederate at the start of the campaign; toward its close the opposing forces were nearly equal.
Catton, Bruce. The Army of the Potomac. Volume 1: Mr. Lincoln's Army. Garden City, N.Y.: Doubleday 1951.
Martin, David G. The Peninsula Campaign, March–July 1862. Conshohocken, Pa.: Combined Books, 1992.
Sears, Stephen W. To the Gates of Richmond: The Peninsula Campaign. New York: Ticknor and Fields, 1992.
Webb, Alexander Stewart. The Peninsula: McClellan's Campaign of 1862. New York: Scribners 1881.
Edwin H.Blanchard/a. r.