By the time he was appointed General-in-Chief, he had nowhere to go. Grant had got him under siege at Petersburg, and he was running out of manpower. He led the Army of Northern Virginia to surrender at Appomattox.
General Robert E. Lee was the leading general of the Confederacy. He was a Virginian who was a West Point graduate. He was enlisted in the US Military at the start of the war, however his loyalty to Virginia and the Confederate cause led him to be the top general of the South. His main command was to lead the Army of Northern Virginia.
Robert E. Lee
No, Major General George Pickett was in command of a division of Longstreet's I Corps in the east with Lee's Army of Northern Virginia. At the time of the Vicksburg Campaign he would have been either in Virginia or later in Pennsylvania fighting at the Battle of Gettysburg.
Although General Lee was unable to lure Union Major General John Pope into a premature battle with the Army of Northern Virginia in the Summer of 1862, Lee created a serious problem for the new Union general who had been called from the Western Theater to lead the Army of Virginia. General Lee directed the reliable Stonewall Jackson to a long march to raid the Army of Virginia's supply depot at Manassas Junction. Stonewall Jackson was successful in his raid on the Union depot. To add another misery to the Pope's situation, Jackson was also able to cut Pope's telegraphic communications to Washington DC.
Robert E. Lee
Based on the failed Peninsula campaign, President Lincoln sought new leadership in the Eastern Theater. He selected Major General John Pope to head the newly created Army of Virginia. To do this, forces from other sources were required. The merger of General Fremont's Mountain Department, General Bank's Department of the Shenandoah, and General McDowell's Department of the Rappahannock. To round out the new army, forces from General Sturgis's Military District of Washington. These sectors combined to form Pope's new army. President Lincoln had great hopes for this combination and he trusted General Pope much more than General McClellan.
No, he was not involved in this battle. General Albert Sidney Johnston was the commander of the Confederate forces. Robert E. Lee had not yet reached his revered status as the Souths consummate general. In fact he would not take command of the Army of Northern Virginia until June 1, 1862 and was serving as a military adviser to Jefferson Davis at the time of the Shiloh battle.
By the end of November 1861, General McClellan believed he had a chance to undermine the Confederate forces in Northern Virginia. McClellan envisioned defeating the Rebel armies in northern Virginia in detail, capturing Richmond and thereby bringing the Southern rebellion to a quick end. To accomplish this, he would need to outflank Confederate forces by landing on the eastern peninsula that would lead to Richmond.
General Gage led the British army in the American Revolutionary War. He was defeated.
Robert E. Lee. Lee was actually reluctant to lead the Confederate forces, but agreed to because he wanted at all cost to protect his beloved Virginia.
General Horatio Gates lead the American army.