All this help, however, was not instantly available. Before it could arrive Rosecrans felt obliged to draw together within the fortifications of Chattanooga, while Bragg quickly closed about him, and, by practically blockading Rosecrans's river communication, placed him in a state of siege. In a few weeks the limited supplies brought the Union army face to face with famine. It having become evident that Rosecrans was incapable of extricating it from its peril, he was relieved and the command given to Thomas, while the three western departments were consolidated under General Grant, and he was ordered personally to proceed to Chattanooga, which place he reached on October 22. Before his arrival, General W.F. Smith had devised and prepared an ingenious plan to regain control of river communication. Under the orders of Grant, Smith successfully executed it, and full rations soon restored vigor and confidence to the Union troops. The considerable reinforcements under Hooker and Sherman coming up, put the besieging enemy on the defensive, and active preparations were begun, which resulted in the famous battle and overwhelming Union victory of Chattanooga on November 23, 24, and 25, 1863. The city of Chattanooga lies on the southeastern bank of the Tennessee River. Back of the city, Chattanooga valley forms a level plain about two miles in width to Missionary Ridge, a narrow mountain range five hundred feet high, generally parallel to the course of the Tennessee, extending far to the southwest. The Confederates had fortified the upper end of Missionary Ridge to a length of five to seven miles opposite the city, lining its long crest with about thirty guns, amply supported by infantry. This formidable barrier was still further strengthened by two lines of rifle-pits, one at the base of Missionary Ridge next to the city, and another with advanced pickets still nearer Chattanooga Northward, the enemy strongly held the end of Missionary Ridge where the railroad tunnel passes through it; southward, they held the yet stronger point of Lookout Mountain, whose rocky base turns the course of the Tennessee River in a short bend to the north. Grant's plan in rough outline was, that Sherman, with the Army of the Tennessee, should storm the northern end of Missionary Ridge at the railroad tunnel; Hooker, stationed at Wauhatchie, thirteen miles to the southwest with his two corps from the Army of the Potomac, should advance toward the city, storming the point of Lookout Mountain on his way; and Thomas, in the city, attack the direct front of Missionary Ridge. The actual beginning slightly varied this program, with a change of corps and divisions, but the detail is not worth noting.