Battle of Chancellorsville
Dilger next went to Howard's headquarters, but was merely told that the Confederate army was retreating and that it was not acceptable to make scouting expeditions without permission of higher-ups. As the sun started to go down, all remained quiet on the XI Corps's front, the noises of the III and XII Corps engaging Lee's rear guard coming from off in the distance.

Around 5:30 p.m., Jackson turned to Robert Rodes and asked him "General, are you ready?" When Rodes nodded, Jackson replied, "You may go forward then."  Most of the men of the XI Corps were encamped and sitting down for supper and had their rifles unloaded and stacked. Their first clue to the impending onslaught was the observation of numerous animals, such as rabbits and foxes, fleeing in their direction out of the western woods. This was followed by the crackle of musket fire, and then the unmistakable scream of the "Rebel Yell".
Two of von Gilsa's regiments, the 153rd Pennsylvania and 54th New York, had been placed up as a heavy skirmish line and the massive Confederate assault rolled completely over them. A few men managed to get off a shot or two before fleeing. The pair of artillery pieces at the very end of the XI Corps line were captured by the Confederates and promptly turned on their former owners. Devens's division collapsed in a matter of minutes, slammed on three sides by almost 30,000 Confederates. Col. Robert Reily and his 75th Ohio managed to resist for about ten minutes before the regiment disintegrated with 150 casualties, including Reily himself, and joined the rest of the fleeing mob.
Col. Lee would later write sarcastically, "A rifle pit is useless when the enemy is on the same side and in rear of your line." Some men tried to stand and resist, but they were knocked over by their fleeing comrades and a hail of Confederate bullets. Maj. Gen. Carl Schurz ordered his division to shift from an east–west alignment to north–south, which they did with amazing precision and speed. They resisted for about 20 minutes and "Leatherbreeches" Dilger managed to drive the Confederates off the turnpike for a bit with his guns, but the sheer weight of Jackson's assault overwhelmed them, too, and they soon had to flee.
Dilger for a time stood alone with a gun firing double-shotted canister at the attackers, then limbered up to flee as the Confederates closed in on him. Three of his artillery horses were shot dead, and when he realized that the gun could not be moved, he had to abandon it. General Howard partially redeemed his inadequate performance prior to the battle by his personal bravery in attempting to rally the troops. He stood shouting and waving a flag held under the stump of his amputated arm lost at the Battle of Seven Pines in 1862, ignoring the danger of the heavy rifle fire, but he could only gather small pockets of soldiers to resist before his corps disintegrated. Col. Adolf Buschbeck's brigade put up a last-ditch stand along with Dilger's guns. They too had to retreat, but maintained good order as they went.
The chaos unfurling on the Union right had gone unnoticed at Hooker's headquarters until at last the sound of gunfire could be heard in the distance, followed by a panic-stricken mob of men and horses pouring into the Chancellorsville clearing. A staff officer yelled "My God, here they come!" as the mob ran to and past the Chancellor mansion. Hooker jumped onto his horse and frantically tried to take action. He ordered Maj. Gen Hiram Berry's division of the III Corps, once his own division, forward, yelling "Receive them on your bayonets!" Artillerymen around the clearing began moving guns into position around Fairview Cemetery.
Meanwhile, down at Hazel Grove, the 8th Pennsylvania Cavalry were relaxing and awaiting orders to chase after Confederate wagon trains, also oblivious to the collapse of the XI Corps. The regiment's commander, Maj. Pennock Huey, received a notice that General Howard was requesting some cavalry. Huey saddled up his men and headed west along the turnpike, where they ran straight into Robert Rodes's division. After a confused fight, the 8th Pennsylvania Cavalry retreated to the safety of the Chancellorsville clearing with the loss of 30 men and three officers.

By nightfall, the Confederate Second Corps had advanced more than 1.25 miles, to within sight of Chancellorsville, but darkness and confusion were taking their toll. The attackers were almost as disorganized as the routed defenders. Although the XI Corps had been defeated, it had retained some coherence as a unit. The corps suffered nearly 2,500 casualties (259 killed, 1,173 wounded, and 994 missing or captured), about one quarter of its strength, including 12 of 23 regimental commanders, which suggests that they fought fiercely during their retreat.
Jackson's force was now separated from Lee's men only by Sickles's corps, which had been separated from the main body of the army after its foray attacking Jackson's column earlier in the afternoon. Like everyone else in the Union army, the III Corps had been unaware of Jackson's attack. When he first heard the news, Sickles was skeptical, but finally believed it and decided to pull back to Hazel Grove.
Sickles became increasingly nervous, knowing that his troops were facing an unknown number of Confederates to the west. A patrol of Jackson's troops was driven back by Union gunners, a minor incident that would come to be exaggerated into a heroic repulse of Jackson's entire command. Between 11 p.m. and midnight, Sickles organized an assault north from Hazel Grove toward the Plank Road, but called it off when his men began suffering artillery and rifle friendly fire from the Union XII Corps.
Stonewall Jackson wanted to press his advantage before Hooker and his army could regain their bearings and plan a counterattack, which might still succeed because of the sheer disparity in numbers. He rode out onto the Plank Road that night to determine the feasibility of a night attack by the light of the full moon, traveling beyond the farthest advance of his men. When one of his staff officers warned him about the dangerous position, Jackson replied, "The danger is all over. The enemy is routed. Go back and tell A.P. Hill to press right on."
As he and his staff started to return, they were incorrectly identified as Union cavalry by men of the 18th North Carolina Infantry, who hit Jackson with friendly fire. Jackson's three bullet wounds were not in themselves life-threatening, but his left arm was broken and had to be amputated. While recovering, he contracted pneumonia and died on May 10. His death was a devastating loss for the Confederacy. Some historians and participants—particularly those of the postbellum Lost Cause movement—attribute the Confederate defeat at Gettysburg two months later to Jackson's absence.
The Union gunners at Fairview Cemetery were alert and nervous; they were a few hundred yards behind Berry's division and still-intact elements of the XI Corps and they found it quite impossible to fire their guns without the shells going over the heads of the infantrymen in front of them. A few friendly-fire casualties resulted from this as the gunners were quick to shoot at anything that looked like enemy soldiers; when they got sight of a large body of Confederates drawing near, they let loose a huge cannonade that landed on and around the party that was carrying the wounded Jackson to the rear and did end up wounding A.P. Hill.

May 3: Chancellorsville: Despite the fame of Stonewall Jackson's victory on May 2, it did not result in a significant military advantage for the Army of Northern Virginia. Howard's XI Corps had been defeated, but the Army of the Potomac remained a potent force and Reynolds's I Corps had arrived overnight, which replaced Howard's losses. About 76,000 Union men faced 43,000 Confederate at the Chancellorsville front. The two halves of Lee's army at Chancellorsville were separated by Sickles's III Corps, which occupied a strong position on high ground at Hazel Grove.
Unless Lee could devise a plan to eject Sickles from Hazel Grove and combine the two halves of his army, he would have little chance of success in assaulting the formidable Union earthworks around Chancellorsville. Fortunately for Lee, Joseph Hooker inadvertently cooperated. 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.