Robert E. Lee had only two advantages: his adversary had surrendered the initiative; and Jacksons May 2 flank attack had the Federals off-balance and reeling. The Union commander, Maj. Gen. Joseph Hooker, had twice the men and materiel of Lee, but he had been too busy fending off relentless Confederate blows to use his resources to land any of his own. Lee crafted a plan for May 3 that would retain the initiative and hopefully reunite his army. Both he and Jeb Stuart would attack at first light. Lee confided to Stuart: It is necessary that the glorious victory thus far achieved be prosecuted with the utmost vigor, and the enemy given no time to rally. He told a staff officer, These people shall be pressed to-day.
Joseph Hooker had to reevaluate all of his plans and intelligence. So far, every prediction, every pronouncement, had been exactly wrong. He had assumed Lee would fly ingloriously from his Rappahannock River defenses as soon as the Union army crossed the stream above and below the Rebel stronghold. Instead, he had provoked Lee to attack on May 1. Hooker announced that Lee was indeed retreating on May 2, only to be blindsided by Stonewall Jacksons onslaught against Maj. Gen. Oliver Otis Howards luckless and isolated XI Corps. It appeared Lee intended to drive Hooker back across the Rappahannock River, but even that now appeared deceptive. Three Confederate riderstwo from A. P. Hills staff and one from Stonewall Jacksonshad been carried into Union lines by frightened mounts, spooked and wounded by the friendly fire that brought down Jackson. Nothing is known of the Rebels interaction with Hooker, though it does appear the Union commander learned of Stonewall Jacksons last order to A. P. Hill: Cut them off from the United States Ford. Union Brig. Gen. Andrew Atkinison Humphreys chronicled, Jackson was aiming, it was said, to get around and take possession of the United States Ford, and thus get in our rear. Brig. Gen. Fitzhugh Lees Confederate cavalry already had disrupted Hookers tie to Elys Ford, lending credence to the notion that Lee intended to cut Hookers line of retreat and destroy the Union army. Well after the fact, it was speculated that cocksure Joseph Hooker had lost his confidence. By the morning of May 3, that seemed evident to at least some of his subordinates. The only thing Hooker knew for certain was that Lee was not done and would attack again as soon as possible.
The Battle of Chancellorsville had become large and ungovernable in the dense woods of the Wilderness, especially at nightand it took on a life of its own that threatened to undo both Lees and Hookers plans. During the black night, the forest exploded repeatedly with a crescendo of action, much to the surprise and consternation of both sides. Maj. Gen. Henry W. Slocums Federal XII Corps had stumbled into Stonewall Jacksons forces that evening around 9:00 p.m. They had fallen back to regroup and assess the situation. Eventually, the Northerners worked their way northeast and tied into the Federal defenses around Fairview and Chancellorsville.
Maj. Gen. Daniel E. Sickles III Corps also attempted to feed back into their old positions along the Orange Turnpike. At midnight, Brig. Gen. David B. Birneys Federal division massed in a large clearing called Hazel Grove and pressed boldly north. Advancing across the open space en masse, the movement of thousands of soldiers by the full moon instantly drew unwanted attention. The jittery XII Corps trusted nothing west of their fortified positions and immediately blistered the darkness with cannon and rifle fire. A. P. Hills Confederates, now led by Brig. Gen. Henry Heth following Hills flesh wound, answered with a crash of musketry. Heths men had nervously rebuffed and captured numerous Yankees throughout the night. To them the woods seemed to be alive with Federals. Their earlier firefight with Slocums XII Corps had resulted in the accidental wounding of Stonewall Jackson. Sickles corps now unwittingly angled into the disputed space between Union and Confederate antagonists, and caught fire from both sides. Human language can give no idea of such a scene, reflected Union Brig. Gen. Alpheus S. Williams, such an infernal and yet sublime combination of sound and flame and smoke, and dreadful yells of rage, or pain, of triumph, or of defiance. More succinctly, a Maine soldier admitted, We were mortally scared! Unable to determine friend from foe in the disorienting darkness, Sickles men backed away and hunkered down at Hazel Grove for the evening. Morning would determine which way they needed to go.