and he could thus move most of his army away from Richmond. This allowed him to relocate Jackson to Gordonsville to block Pope and protect the Virginia Central. Lee had larger plans in mind. Since the Union Army was split between McClellan and Pope and they were widely separated, Lee saw an opportunity to destroy Pope before returning his attention to McClellan. Initial movements On July 26, Lee met with cavalry commander and partisan fighter Capt. John S. Mosby, who had just been exchanged as a prisoner of war. Coming through the Hampton Roads area in Union custody, Mosby observed significant naval transport activity and deduced that Maj. Gen. Ambrose Burnside's troops, who had fought in North Carolina, were being shipped to reinforce Pope. Wanting to take immediate action before those troops were in position, the next day Lee committed Maj. Gen. A.P. Hill to join Jackson with 12,000 men, while distracting McClellan with artillery bombardments and diversionary movements. McClellan advanced a force from Harrison's Landing to Malvern Hill, and Lee moved south to meet the threat, but McClellan eventually withdrew his advance. Still convinced that he was heavily outnumbered, he sent messages to Washington that he would need at least 50,000 more men before he could attempt another attack on Richmond. On August 3, General-in-Chief Henry W. Halleck directed McClellan to begin his final withdrawal from the Peninsula and to return to Northern Virginia to support Pope. McClellan protested and did not begin his redeployment until August 14. The Army of the Potomac returned to Washington except for a division of the IV Corps, which was left on the Virginia Peninsula. Opposing forces Union Confederate Battles and movements On July 29, Pope moved his headquarters from Washington to the field. He was informed by Halleck of the plan to link up with McClellan's army, but rather than waiting for this to occur, he moved some of his forces to a position near Cedar Mountain, from whence he could launch cavalry raids on Gordonsville. Jackson advanced to Culpeper Court House on August 7, hoping to attack one of Pope's corps before the rest of the army could be concentrated. Cedar Mountain On August 9, Nathaniel Banks's corps attacked Jackson at Cedar Mountain, gaining an early advantage. Confederate Brig. Gen. Charles S. Winder was killed and his division mauled. A Confederate counterattack led by Maj. Gen. A.P. Hill drove Banks back