September 19-20, 1863

A decisive Confederate victory by Gen. Braxton Bragg's Army of Tennessee at Chickamauga leaves Gen. William S. Rosecrans Union Army of the Cumberland trapped in Chattanooga, Tenn. under Confederate siege. During the night preceding the battle both sides were shifting troops. Neither army knew the exact position of the other. It's probable that division commanders on either side hardly knew where their own commands were, in the thick woods, much less those of the enemy. On the morning of the 19th Thomas ordered Brannan's division, then posted on the road 2 miles north of the Lee and Gordon's Mill, to reconnoiter toward Chickamauga Creek. Brannan encountered, and drove back Forrest's unmounted cavalry, which called on the nearest Confederate infantry for help. This began an all day battle. Every division of the 16th, 20th and 21st Corps were committed. Of the Confederate forces, only the divisions of Breckinridge and Hindman, on the south flank, were not involved. Neither side gained any decided advantage. During the night the two opposing forces further rearranged their dispositions in the difficult terrain. Rosecrans prepared defensive positions, while Bragg planned his attack. Longstreet had arrived during the night and was given command of the left wing of Bragg's Army. Polk was given command of the other wing. Bragg's units were to attack successively from the north and south. At 9:00 am, Breckinridge attacked. Thomas, commanding the Federal west wing, called for Negley's division, which was supposed to be in reserve. However, due to an error, Negley was in the line. Wood, whose division was to be in reserve of Negley's division, moved up to relieve Negley, while the latter sent one brigade and then another to reinforce Thomas. For 2 hours, the Federal left held off heavy attacks. Rosecrans misunderstanding as to the true location of his units led to a fatal error. He was trying to strengthen his defenses on his right while Thomas held the other flank. Thinking Woods was on Reynold's flank, he ordered Wood to "close up and support Reynolds." Actually, it was Brannon on Wood's left, and following his instructions, Wood pulled out of the line, passed behind Brannan, and fell in on Reynold's flank. The divisions of Sheridan and J.C. Davis were closing to fill this gap at 11:30 when Longstreet attacked. By a strange coincidence, Longstreet hit the precise point left open by the fatal error. Sheridan's and Davis's divisions were shattered by superior force, and the Federal right was driven back on its left flank. Rosecrans, Crittenden, and McCook, unable to rally the troops around them, fled to Chattanooga, thinking the entire army was being destroyed. Thomas remained on the field, turning Wood and Branna to block Longstreet on the south. Bragg had failed to provide for a general, and so was unable to exploit Longstreet's success. Three brigades of Granger's Reserve Corps (Army of the Kentucky) were near McAffee's Church with orders to remain there and protect the flank. In a terrific example of battlefield initiative Granger violated his orders "at the moment of greatest need reported to Gen. Thomas with 2 brigades." Van Horne says, "the opportune aid of these 2 brigades saved the army from defeat and rout." Thomas held the field until dark then, on orders from Rosecrans, withdrew to Rossville Gap. Rosecrans withdrew his army into the defenses of Chattanooga. Bragg followed, and occupied Missionary Ridge and laid siege to the town.