Following the Battle of the Wilderness, Lieut. Gen. Ulysses S. Grant marched the Union army south with the hope of capturing Spotsylvania Court House and preventing Robert E. Lee's army from retreating further. Lee's Confederates, however, managed to get ahead of the Federals and block the road. Fighting began on May 8th, when the Union Fifth Corps under Maj. Gen. Gouverneur K. Warren and the Sixth Corps under Maj. Gen. John Sedgwick engaged Confederate Maj. Gen. Richard Anderson's First Corps at Laurel Hill near the road to the Court House. The Rebels were able to hold the hill and extend their lines further east into a salient known as the Mule Shoe. On May 10th, Grant attacked both Laurel Hill and the Mule Shoe with elements of three Union army corps. An innovative, compact, 12-regiment attacking column led by Colonel Emory Upton nearly achieved success against the heavily entrenched Confederates but was beaten back. Grant added Maj. Gen. Ambrose E. Burnside's Ninth Corps to the fight, adding pressure to the Confederate right flank. On the 11th, Grant and Lee consolidated their lines. At 4:30am on the 12th, the Union Second Corps under Maj. Gen. Winfield S. Hancock attacked the Mule Shoe salient in some of the most violent fighting of the war. Burnside on the left and Warren on the right attacked as well. Timely Confederate reinforcements constructed a new defensive line at the base of the Mule Shoe. Bloody hand-to-hand fighting continued until the Confederates withdrew early on the 13th. Grant shifted his lines again and reattacked on the 18th. Lee withdrew to the North Anna River the night of May 20th, beginning the next phase of the Overland Campaign.