George B. McClellan rebuilt the Army of the Potomac after First Bull Run, ringing Washington with 48 forts and 480 heavy guns, and in November 1861 told Lincoln he could do it all as general-in-chief. Instead of marching overland, he pushed his Urbanna Plan to move the army by water around the Confederates, defending it in a 22-page letter to the president. Joseph E. Johnston withdrew in March 1862, leaving behind Quaker guns, and Lincoln removed McClellan as general-in-chief on March 11.

McClellan shipped more than 120,000 men, 15,000 horses, and 1,150 wagons to Fort Monroe, but the CSS Virginia kept the Navy from covering his flanks. At the Warwick Line, John B. Magruder’s roughly 11,000 men held him for a month while Allan Pinkerton’s inflated estimates put the enemy near 100,000. The episode follows Williamsburg, Hanover Court House, Seven Pines and the Grapevine Bridge, Johnston’s wounding, Robert E. Lee’s arrival, and the retreat to the James River after Malvern Hill.

• Magruder marched a single company in a continuous loop through a clearing to simulate endless reinforcements.
• McClellan prepared more than 70 siege guns, and the Confederates left the night before the bombardment.
• He dismissed escaped enslaved people who reported that the Confederates were evacuating their lines.
• Edwin Sumner’s men crossed the Grapevine Bridge at Seven Pines just before it washed away.
• J.E.B. Stuart’s cavalry rode completely around the Union army in three days.