[Illustration: WAR IN THE WEST, 1863-65, AND ON THE COAST.] CHICKAMAUGA, 1863.--While Grant was besieging Vicksburg, Rosecrans forced a Confederate army under Bragg to quit its position south of Murfreesboro, and then to leave Chattanooga and retire into northern Georgia. There Bragg was reënforced, and he then attacked Rosecrans in the Chickamauga valley (September 19 and 20, 1863), where was fought one of the most desperate battles of the war. The Union right wing was driven from the field, but the left wing under General Thomas held the enemy in check and saved the army from rout. By his firmness Thomas won the name of "the Rock of Chickamauga." CHATTANOOGA.--Rosecrans now went back to Chattanooga. Bragg followed, and, taking position on the hills and mountains which surround the town on the east and south, shut in the Union army and besieged it. Hooker was sent from Virginia with more troops, Sherman [4] brought an army from Vicksburg, Rosecrans was replaced by Thomas, and Grant was put in command of all. Then matters changed. The troops under Thomas (November 23) seized some low hills at the foot of Missionary Ridge, east of Chattanooga. Hooker (November 24) carried the Confederate works on Lookout Mountain, southwest of the town, in a fight often called "the Battle above the Clouds." Sherman (November 24 and 25) attacked the northern end of Missionary Ridge. Thomas (November 25) thereupon carried the heights of Missionary Ridge, and drove off the enemy. Bragg retreated to Dalton in northwestern Georgia, where the command of his army was given to General J. E. Johnston. [Illustration: WILLIAM T. SHERMAN.] [Illustration: CHARGING UP MISSIONARY RIDGE.] THE PLAN OF CAMPAIGN, 1864.--The Confederates had now but two great armies left. One under Lee was lying quietly behind the Rappahannock and Rapidan rivers, protecting Richmond; the other under J. E. Johnston [5] was at Dalton, Georgia. The two generals chosen to lead the Union armies against these forces were Grant and Sherman. Grant (now lieutenant general arid in command of all the armies) with the Army of the Potomac was to drive Lee back and take Richmond. Sherman with the forces under Thomas, McPherson, and Schofield was to attack Johnston and enter Georgia. The Union soldiers outnumbered the Confederates. [Illustration: JOSEPH E. JOHNSTON.] MARCHING THROUGH GEORGIA.--On May 4, 1864, accordingly, Sherman moved forward against Johnston, flanked him out of Dalton, and drove him, step by step, through the mountains to Atlanta. Johnston's retreat forced Sherman to weaken his army by leaving guards in the rear to protect the railroads on which he depended for supplies; Johnston intended to attack when he could fight on equal terms. But his retreat displeased Davis, and at Atlanta he was replaced by General Hood, who was expected to fight at once.