Crawfish Spring, to the South of the Chickamauga Battle-field. Rosecrans, in concentrating his troops on the 18th of September, was still possessed of the idea that Bragg was covering his retreat upon his railroad connections at Dalton. Instead, the Confederate commander had massed his forces on the other side of Chickamauga and was only awaiting the arrival of Longstreet to assume the aggressive. On the morning of the 19th, McCook's right wing at Crawfish Spring was strongly threatened by the Confederates, while the real attack was made against the left in an effort to turn it and cut Rosecrans off from a retreat upon Chattanooga. All day long, brigade after brigade was marched from the right of the Federal line in order to extend the left under Thomas and withstand this flanking movement. Even after nightfall, Thomas, trying to re-form his lines and carry them still farther to the left for the work of the morrow, brought on a sharp conflict in the darkness. The Confederates had been held back, but at heavy cost. That night, at the Widow Glenn's house, Rosecrans consulted his generals. The exhausted Thomas, when roused from sleep for his opinion, invariably answered, "I would strengthen the left." There seemed as yet to be no crisis at hand, and the council closed with a song by the debonair McCook. [Illustration: WHERE THE LINES WERE SWEPT BACK COPYRIGHT, 1911, REVIEW OF REVIEWS CO.] Lee & Gordon's mill, seen in the picture, marked the extreme right of the Federal line on the second day at Chickamauga. From it, northward, were posted the commands of McCook and Crittenden, depleted by the detachments of troops the day before to strengthen the left. All might have gone well if the main attack of the Confederates had continued to the left, as Rosecrans expected. But hidden in the woods, almost within a stone's throw of the Federal right on that misty morning, was the entire corps of Longstreet, drawn up in columns of brigades at half distance--"a masterpiece of tactics," giving space for each column to swing right or left. Seizing a momentous opportunity which would have lasted but thirty minutes at the most, Longstreet hurled them through a gap which, owing to a misunderstanding, had been left open, and the entire Federal right was swept from the field. [Illustration: THE HOUSE WHENCE HELP CAME COPYRIGHT, 1911, REVIEW OF REVIEWS CO.]