At last, after much fruitless manoeuvring, the collision took place, and for two days there was fierce and stubborn fighting on the famous battlefield of Chickamauga. On the second day, September 20, Longstreet, commanding the Confederate left, thoroughly defeated the Federal right and centre and sent them in precipitate flight to Chattanooga. Rosecrans, overwhelmed amid the rush of fugitives, and thinking that all was lost, also hastened thither to take charge of the fragments. In truth all would have been lost, had it not been for Thomas. This able and resolute commander won in this fight the rhetorical but well merited name of "the Rock of Chickamauga." Under him the Federal left stood immovable, though furiously assailed by odds, and tried by the rout of their comrades. At nightfall these troops, still in position, covered the withdrawal to Chattanooga. Rosecrans, badly demoralized, gave the President to understand that there had been a terrible disaster, and the President, according to his custom in such trying moments, responded with words of encouragement and an instant effort to restore morale. Mr. Lincoln always cheered his generals in the hour of disaster, which he seemed to regard only as the starting-point for a new advance, the incentive to a fresh exertion. Yet, in fact, there had not been a disaster, but only a moderate worsting of the Federal army, resulting in its retirement a trifling distance to the place whence its opponents had just marched out. The issue between the two generals was still as open after Rosecrans's misfortune as it had been after the previous misfortunes of Bragg. Already there was a new question, who would win that coming battle which plainly was close at hand. The curtain had only gone down on an act; the drama itself had not been played out. Bragg advanced to besiege Chattanooga, and Rosecrans's communications were so imperfect that his troops were put on short rations. On the other hand, Mr. Lincoln bestirred himself vigorously. He promptly sent Sherman from the West, and Hooker from the East, each with considerable reinforcements, en route for the beleaguered town. Also he saw plainly that, whether by fault or misfortune, the usefulness of Rosecrans was over, and on October 16 he put Thomas in place of Rosecrans,[47] and gave to General Grant the command of the Military Division of the Mississippi, including the Departments of the Ohio, the Cumberland, and the Tennessee. Grant at once telegraphed to Thomas to hold Chattanooga at all hazards; to which Thomas replied: "We will hold the town till we starve!" Grant well knew that they were already getting very hungry. He showed his usual prompt energy in relieving them; and a little fighting soon opened a route by which sufficient food came into the place.