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In the Eastern Theater of the American Civil War, the objective of the Union had been to advance and seize the Confederate capital, Richmond, Virginia. In the first two years of the war, four major attempts had failed: the first foundered just miles away from Washington, D.C., at the First Battle of Bull Run (First Manassas) in July 1861. Maj. Gen. George B. McClellan's Peninsula Campaign took an amphibious approach, landing his Army of the Potomac on the Virginia Peninsula in the spring of 1862 and coming within  of Richmond before being turned back by Gen. Robert E. Lee in the Seven Days Battles. That summer, Maj. Gen. John Pope's Army of Virginia was defeated at the Second Battle of Bull Run. In December 1862, Maj. Gen. Ambrose Burnside commanded the Army of the Potomac and attempted to reach Richmond by way of Fredericksburg, Virginia, where he was defeated at the Battle of Fredericksburg. This string of Union defeats was interrupted in September 1862 when Lee moved into Maryland and his campaign was turned back by McClellan at the Battle of Antietam, but this represented no threat to Richmond.

In January 1863, the Army of the Potomac, following the Battle of Fredericksburg and the humiliating Mud March, suffered from rising desertions and plunging morale. Maj. Gen. Ambrose Burnside decided to conduct a mass purge of the Army of the Potomac's leadership, eliminating a number of generals who he felt were responsible for the disaster at Fredericksburg. In reality, he had no power to dismiss anyone without the approval of Congress. Predictably, Burnside's purge went nowhere, and he offered President Abraham Lincoln his resignation from command of the Army of the Potomac. He even offered to resign entirely from the Army, but the president persuaded him to stay, transferring him to the Western Theater, where he became commander of the Department of the Ohio. Burnside's former command, the IX Corps, was transferred to the Virginia Peninsula, a movement that prompted the Confederates to detach troops from Lee's army under Lt. Gen. James Longstreet, a decision that would be consequential in the upcoming campaign.

Abraham Lincoln had become convinced that the appropriate objective for his Eastern army was the army of Robert E. Lee's, not any geographic features such as a capital city, but he and his generals knew that the most reliable way to bring Lee to a decisive battle was to threaten his capital. Lincoln tried a fifth time with a new general on January 25, 1863—Maj. Gen. Joseph Hooker, a man with a pugnacious reputation who had performed well in previous subordinate commands.

With Burnside's departure, Maj. Gen. William B. Franklin left as well. Franklin had been a staunch supporter of George B. McClellan and refused to serve under Hooker, because he disliked him personally and also because he was senior to Hooker in rank. Maj. Gen. Edwin V. Sumner stepped down due to old age (he was 65) and poor health. He was reassigned to a command in Missouri, but died before he could assume it. Brig. Gen. Daniel Butterfield was reassigned from command of the V Corps to be Hooker's chief of staff.

Hooker embarked on a much-needed reorganization of the army, doing away with Burnside's grand division system, which had proved unwieldy; he also no longer had sufficient senior officers on hand that he could trust to command multi-corps operations. He organized the cavalry into a separate corps under the command of Brig. Gen. George Stoneman (who had commanded the III Corps at Fredericksburg). But while he concentrated the cavalry into a single organization, he dispersed his artillery battalions to the control of the infantry division commanders, removing the coordinating influence of the army's artillery chief, Brig. Gen. Henry J. Hunt.

Hooker established a reputation as an outstanding administrator and restored the morale of his soldiers, which had plummeted to a new low under Burnside. Among his changes were fixes to the daily diet of the troops, camp sanitary changes, improvements and accountability of the quartermaster system, addition of and monitoring of company cooks, several hospital reforms, an improved furlough system, orders to stem rising desertion, improved drills, and stronger officer training.