While we were thus lying idle in camp on the big Black, the Army of the Cumberland, under General Rosecrans, was moving against Bragg at Chattanooga; and the Army of the Ohio, General Burnside, was marching toward East Tennessee. General Rosecrans was so confident of success that he somewhat scattered his command, seemingly to surround and capture Bragg in Chattanooga; but the latter, reenforced from Virginia, drew out of Chattanooga, concentrated his army at Lafayette, and at Chickamauga fell on Rosecrans, defeated him, and drove him into Chattanooga. The whole country seemed paralyzed by this unhappy event; and the authorities in Washington were thoroughly stampeded. From the East the Eleventh Corps (Slocum), and the Twelfth Corps (Howard), were sent by rail to Nashville, and forward under command of General Hooker; orders were also sent to General Grant, by Halleck, to send what reenforcements he could spare immediately toward Chattanooga.
Bragg had completely driven Rosecrans’s army into Chattanooga; the latter was in actual danger of starvation, and the railroad to his rear seemed inadequate to his supply. The first intimation which I got of this disaster was on the 22d of September, by an order from General Grant to dispatch one of my divisions immediately into Vicksburg, to go toward Chattanooga, and I designated the First, General Osterhaus—Steele meantime having been appointed to the command of the Department of Arkansas, and had gone to Little Rock. General Osterhaus marched the same day, and on the 23d I was summoned to Vicksburg in person, where General Grant showed me the alarming dispatches from General Halleck, which had been sent from Memphis by General Hurlbut, and said, on further thought, that he would send me and my whole corps. But, inasmuch as one division of McPherson’s corps (John E. Smith’s) had already started, he instructed me to leave one of my divisions on the Big Black, and to get the other two ready to follow at once. I designated the Second, then commanded by Brigadier-General Giles A. Smith, and the Fourth, commanded by Brigadier-General Corse.