After taking heavy losses at Cold Harbor, Lt. Gen. Grant decided to move his army across the James River and attack Petersburg, whose capture and key rail links would cut off Richmond from the rest of the Confederacy. On June 9, as Grant prepared to move from Cold Harbor, he ordered the 10th Corps under Maj. Gen. Quincy A. Gillmore to attack Petersburg from Bermuda Hundred, but Confederate resistance was strong enough to make Gillmore halt the attack. On June 12-13, Grant pulled his army out of Cold Harbor and began moving to the James River. On June 15, the 18th Corps under Gen. William F. “Baldy” Smith crossed the Appomattox River at Point of Rocks and captured more than a mile of the Dimmock Line in front of Petersburg, but rumors of Confederate reinforcements caused Smith to stop his advance as Confederate Gen. P.G.T. Beauregard began withdrawing troops from the Howlett Line in Bermuda Hundred to defend Petersburg. On June 16, the 2nd Corps under Maj. Gen. Winfield Scott Hancock continued the attack on Petersburg, while in Bermuda Hundred the Federals captured the abandoned Howlett Line before Confederate reinforcements retook it that evening. On June 17, the 2nd Corps continued its attack on Petersburg joined by the 9th Corps under Maj. Gen. Ambrose E. Burnside. By June 18, Grant had the bulk of his army across the James River, and a third Union assault by the 1st, 2nd, and 9th Corps failed to break through the Confederate line. The failure to capture Petersburg quickly led to 10 long months of siege warfare, marked the end of the Bermuda Hundred Campaign, and left the Army of the James under Grant’s direction, with Maj. Gen. Butler no longer holding an independent command.