Disaster to the Union army had been averted by the use of powerful artillery when the infantry seemed unable to withstand the onslaught. Rosecrans had assumed the defensive, and his troops had so far receded as to enable the Confederates to form their lines on all the territory fought over on that day. During the night preparations were made in both camps for a renewal of the battle on the following morning, which was Sunday. A fresh disposition of the troops was made by both leaders. Near midnight General Longstreet arrived on the field, and was once placed in command of the Confederate left, Polk retaining the right. Not all of Longstreet's troops arrived in time for the battle, but Bragg's force has been estimated at fifty-one to seventy-one thousand strong. Thomas was given command of the Union left, with McCook at his right, while Crittenden's forces occupied the center, but to the rear of both Thomas and McCook. Thomas had spent the night in throwing up breastworks on the brow of Snodgrass Hill, as it was anticipated that the Confederates would concentrate their attack upon his position. Hostilities began with a general movement of the Confederate right wing in an attempt to flank the Union left. General Bragg had ordered Polk to begin the attack at daybreak, but it was nearly ten o'clock in the morning before Breckinridge's division, supported by General Cleburne, advanced upon Thomas' entrenchments. Fighting desperately, the Confederates did not falter under the heavy fire of the Federals, and it seemed as if the latter must be driven from their position. Rosecrans, in response to urgent requests for reënforcements, despatched troops again and again to the aid of Thomas, and the assault was finally repulsed. Cleburne's division was driven back with heavy loss, and Breckinridge, unable to retain any advantage, was forced to defend his right, which was being seriously menaced. The battle at this point had been desperately waged, both sides exhibiting marked courage and determination. As on the previous day, the Confederates had been the aggressors, but the Federal troops had resisted all attempts to invade their breastworks.