Battle of Chancellorsville
Early on May 3, Hooker ordered Sickles to move from Hazel Grove to a new position on the Plank Road. As they were withdrawing, the trailing elements of Sickles's corps were attacked by the Confederate brigade of Brig. Gen. James J. Archer, which captured about 100 prisoners and four cannons. Hazel Grove was soon turned into a powerful artillery platform with 30 guns under Col. Porter Alexander.
After Jackson was wounded on May 2, command of the Second Corps fell to his senior division commander, Maj. Gen. A.P. Hill. Hill was soon wounded himself. He consulted with Brig. Gen. Robert E. Rodes, the next most senior general in the corps, and Rodes acquiesced in Hill's decision to summon Maj. Gen. J.E.B. Stuart to take command, notifying Lee after the fact. Brig. Gen. Henry Heth replaced Hill in division command.
Although Stuart was a cavalryman who had never commanded infantry before, he was to deliver a creditable performance at Chancellorsville. By the morning of May 3, the Union line resembled a horseshoe. The center was held by the III, XII, and II Corps. On the left were the remnants of the XI Corps, and the right was held by the V and I Corps. On the western side of the Chancellorsville salient, Stuart organized his three divisions to straddle the Plank Road: Heth's in the advance, Colston's 300–500 yards behind, and Rodes's, whose men had done the hardest fighting on May 2, near the Wilderness Church.
The attack began about 5:30 a.m. supported by the newly installed artillery at Hazel Grove, and by simultaneous attacks by the divisions of Anderson and McLaws from the south and southeast. The Confederates were resisted fiercely by the Union troops behind strong earthworks, and the fighting on May 3 was the heaviest of the campaign. The initial waves of assaults by Heth and Colston gained a little ground, but were beaten back by Union counterattacks.

Rodes sent his men in last and this final push, along with the excellent performance of the Confederate artillery, carried the morning battle. Chancellorsville was the only occasion in the war in Virginia in which Confederate gunners held a decided advantage over their Federal counterparts. Confederate guns on Hazel Grove were joined by 20 more on the Plank Road to duel effectively with the Union guns on neighboring Fairview Hill, causing the Federals to withdraw as ammunition ran low and Confederate infantrymen picked off the gun crews.
Fairview was evacuated at 9:30 a.m., briefly recaptured in a counterattack, but by 10 a.m. Hooker ordered it abandoned for good. The loss of this artillery platform doomed the Union position at the Chancellorsville crossroads as well, and the Army of the Potomac began a fighting retreat to positions circling United States Ford. The soldiers of the two halves of Lee's army reunited shortly after 10 a.m. before the Chancellor mansion, wildly triumphant as Lee arrived on Traveller to survey the scene of his victory.

Lee's presence was the signal for one of those uncontrollable bursts of enthusiasm which none can appreciate who has not witnessed them. The fierce soldiers, with their faces blackened with the smoke of battle, the wounded crawling with feeble limbs from the fury of the devouring flames, all seemed possessed with a common impulse. One long unbroken cheer, in which the feeble cry of those who lay helpless on the earth blended with the strong voices of those who still fought, rose high above the roar of battle and hailed the presence of a victorious chief. He sat in the full realization of all that soldiers dream of—triumph; and as I looked at him in the complete fruition of the success which his genius, courage, and confidence in his army had won, I thought that it must have been from some such scene that men in ancient days ascended to the dignity of gods.
At the height of the fighting on May 3, Hooker suffered an injury when at 9:15 a.m. a Confederate cannonball hit a wooden pillar he was leaning against at his headquarters. He later wrote that half of the pillar "violently [struck me] ... in an erect position from my head to my feet." He likely received a concussion, which was sufficiently severe to render him unconscious for over an hour. Although clearly incapacitated after he arose, Hooker refused to turn over command temporarily to his second-in-command, Maj. Gen. Darius N. Couch, and, with Hooker's chief of staff, Maj. Gen. Daniel Butterfield, and Sedgwick out of communication (again due to the failure of the telegraph lines), there was no one at headquarters with sufficient rank or stature to convince Hooker otherwise. This failure may have affected Union performance over the next day and may have directly contributed to Hooker's seeming lack of nerve and timid performance throughout the rest of the battle.
Meanwhile, at about 7:30 a.m., near Chancellorsville, III Corps, Second Division commander Maj. Gen. Hiram Berry was killed by Confederate musket fire. Brig. Gen. Gershom Mott, next in seniority, was also severely wounded at about that time. Believing himself to be next in command, Brig. Gen. Joseph Warren Revere (grandson of Paul Revere) assumed command of the division. Finding himself in among stragglers from the battle and unable to contact Sickles, Revere commanded a group of 500 or 600 soldiers to reform at a point about three miles to the north of Chancellorsville. This three-mile march away from the battlefield, described by Revere as a "regrouping effort" and not a retreat, led to his being court-martialed in August by Maj. Gen. Hooker. This coincided with Revere's friendly 1852 conversation with Stonewall Jackson, in which Jackson used horoscopes and astrology to predict Revere's "culmination of the malign aspect" in the first days of May 1863.

May 3: Fredericksburg and Salem Church: As Lee was savoring his victory at the Chancellorsville crossroads, he received disturbing news: Maj. Gen. John Sedgwick's force had broken through the Confederate lines at Fredericksburg and was headed toward Chancellorsville. On the night of May 2, in the aftermath of Jackson's flank attack, Hooker had ordered Sedgwick to "cross the Rappahannock at Fredericksburg on the receipt of this order, and at once take up your line of march on the Chancellorsville road until you connect with him. You will attack and destroy any force you may fall in with on the road."
Lee had left a relatively small force at Fredericksburg, ordering Brig. Gen. Jubal Early to "watch the enemy and try to hold him." If he was attacked in "overwhelming numbers," Early was to retreat to Richmond, but if Sedgwick withdrew from his front, he was to join with Lee at Chancellorsville. On the morning of May 2, Early received a garbled message from Lee's staff that caused him to start marching most of his men toward Chancellorsville, but he quickly returned after a warning from Brig. Gen. William Barksdale of a Union advance against Fredericksburg.
At 7 a.m. on May 3, Early was confronted with four Union divisions: Brig. Gen. John Gibbon of the II Corps had crossed the Rappahannock north of town, and three divisions of Sedgwick's VI Corps—Maj. Gen. John Newton and Brig. Gens. Albion P. Howe and William T. H. Brooks—were arrayed in line from the front of the town to Deep Run. Most of Early's combat strength was deployed to the south of town, where Federal troops had achieved their most significant successes during the December battle. Marye's Heights was defended by Barksdale's Mississippi brigade and Early ordered the Louisiana brigade of Brig. Gen. Harry T. Hays from the far right to Barksdale's left.

By midmorning, two Union attacks against the infamous stone wall on Marye's Heights were repulsed with numerous casualties. A Union party under flag of truce was allowed to approach ostensibly to collect the wounded, but while close to the stone wall, they were able to observe how sparsely the Confederate line was manned. A third Union attack was successful in overrunning the Confederate position. Early was able to organize an effective fighting retreat.
John Sedgwick's road to Chancellorsville was open, but he wasted time in gathering his troops and forming a marching column. His men, led by Brooks's division, followed by Newton and Howe, were delayed for several hours by successive actions against the Alabama brigade of Brig. Gen. Cadmus M. Wilcox. His final delaying line was a ridge at Salem church, where he was joined by three brigades from McLaws's division and one from Anderson's, bringing the total Confederate strength to about 10,000 men.