throughout the war, but Grant was the first general who actively cooperated with it. As their campaigns progressed, however, the political importance of the cities of Richmond and Atlanta began to dominate their strategy. By 1864, Atlanta was a critical target. The city of 20,000 was founded at the intersection of four important railroad lines that supplied the Confederacy and was a military manufacturing arsenal in its own right. Atlanta's nickname of "Gate City of the South" was apt—its capture would open virtually the entire Deep South to Union conquest. Grant's orders to Sherman were to "move against Johnston's Army, to break it up and to get into the interior of the enemy's country as far as you can, inflicting all the damage you can against their war resources." Sherman's force of about 100,000 men was composed of three subordinate armies: the Army of the Tennessee (Grant's and later Sherman's army of 1862–63) under Maj. Gen. James B. McPherson; the Army of the Cumberland under Maj. Gen. George H. Thomas; and the relatively small Army of the Ohio (composed of only the XXIII Corps) under Maj. Gen. John M. Schofield. Their principal opponent was the Confederate Army of Tennessee, commanded by Gen. Joseph E. Johnston, who had replaced the unpopular Braxton Bragg after his defeat in Chattanooga in November 1863. The 50,000-man army consisted of the infantry corps of Lt. Gens. William J. Hardee, John Bell Hood, and Leonidas Polk, and a cavalry corps under Maj. Gen. Joseph Wheeler. Start of the Atlanta campaign Sherman's campaign began on May 7, as his three armies departed from the vicinity of Chattanooga. He launched demonstration attacks against Johnston's position on the long, high mountain named Rocky Face Ridge while McPherson's Army of the Tennessee advanced stealthily around Johnston's left flank toward the town of Resaca and Johnston's supply line on the Western & Atlantic Railroad. Unfortunately for Sherman, McPherson encountered a small Confederate force entrenched in the outskirts of Resaca and cautiously pulled back to Snake Creek Gap, squandering the opportunity to trap the Confederate army. As Sherman swung his entire army in the direction of Resaca, Johnston retired to take up positions there. Full scale fighting erupted in the Battle of Resaca on May 14–15 but there was no conclusive result and Sherman flanked Johnston for a second time by crossing the Oostanaula River. As Johnston withdrew again, skirmishing erupted at