Creek, Lee was free to shift Breckinridge's division to his far right flank. He also moved troops from A. P. Hill's Third Corps, the divisions of Brig. Gens. William Mahone and Cadmus M. Wilcox, to support Breckinridge, and stationed cavalry under Fitzhugh Lee to guard the army's right flank. The result was a curving line on low ridges, long, with the left flank anchored on Totopotomoy Creek, the right on the Chickahominy River, making any flanking moves impossible. Lee's engineers used their time effectively and constructed the "most ingenious defensive configuration the war had yet witnessed." At 4:30 a.m. on June 3, the three Union corps began to advance through a thick ground fog. Massive fire from the Confederate lines quickly caused heavy casualties, and the survivors were pinned down. The most effective performance of the day was on the Union left flank, where Hancock's corps was able to break through a portion of Breckinridge's front line and drive those defenders out of their entrenchments in hand-to-hand fighting. However, nearby Confederate artillery turned the entrenchments into a death trap for the Federals. Breckinridge's reserves counterattacked these men from the division of Brig. Gen. Francis C. Barlow and drove them off. Hancock's other advanced division, under Brig. Gen. John Gibbon, became disordered in swampy ground and could not advance through the heavy Confederate fire. One of Gibbon's men, complaining of a lack of reconnaissance, wrote, "We felt it was murder, not war, or at best a very serious mistake had been made." In the center, Wright's corps was pinned down by the heavy fire and made little effort to advance further, still recovering from their costly charge on June 1. On the Union right, Smith's men advanced through unfavorable terrain and were channeled into two ravines. When they emerged in front of the Confederate line, rifle and artillery fire mowed them down. The artillery fire against Smith's corps was heavier than might have been expected because Warren's V Corps to his right was reluctant to advance and the Confederate gunners in Warren's sector concentrated on Smith's men instead. The only activity on the northern end of the field was by Burnside's IX Corps, facing Jubal Early. He launched a powerful assault at 6 a.m. that overran the Confederate skirmishers but mistakenly thought he had pierced the first line of earthworks and halted his corps to regroup before moving on, which he