 In spring 1862 , Union commander Maj. Gen. George B. McClellan developed an ambitious plan to capture Richmond , the Confederate capital , on the Virginia Peninsula . His 121 @,@ 500 @-@ man Army of the Potomac , along with 14 @,@ 592 animals , 1 @,@ 224 wagons and ambulances , and 44 artillery batteries , would load onto 389 vessels and sail to the tip of the peninsula at Fort Monroe , then move inland and capture the capital . The bold and sweeping landing was executed with few incidents , but the Federals were delayed for about a month in the Siege of Yorktown . When McClellan 's army finally did attack on May 4 , the defensive earthworks around Yorktown were undefended . After some hours , the Army of the Potomac pursued the retreating Confederates . When Union troops encountered the Confederate rearguard at Williamsburg , the two armies fought an inconclusive battle . The Confederates continued their withdrawal that night . To stymie the Southerners ' retreat , McClellan sent Brig. Gen. William F. " Baldy " Smith to Eltham 's Landing by boat , resulting in a battle there on May 7 . When the Union Army tried to attack Richmond by way of the James River , they were turned back at Drewry 's Bluff on May 15 . All the while , McClellan continued his pursuit of Confederate forces , who were withdrawing quickly towards Richmond . 
