After a careful reading of the letter, the chief-of-staff said, quietly, but firmly,-- "It will never do, General. _We_ don't want to whip by such means. If the slaves, of their own accord, rise and assert their original right to themselves, that will be their own affair; but we can have no complicity with them without outraging the moral sense of the civilized world." "But what if the other departments should encourage these uprisings?" "We must do all in our power to prevent them," exclaimed Garfield. Rosecrans, whose confidence in his chief-of-staff was daily increasing, immediately took measures to stop the movement, and the insurrection, with all its attendant horrors, was averted. To Garfield was now submitted the task of planning some movement which would oblige Bragg to leave Chattanooga. General Halleck, then in Washington at the head of the War Department, had sent to Rosecrans the following telegram,-- "The orders for the advance of your army are peremptory." The only movement that could be made with any advantage at this time, would be for the Union army to cross the river in three divisions and cut off Bragg from all communication with Atlanta, whence he was expecting supplies and reinforcements. Pontoons were, therefore, brought forward, and materials prepared for building a couple of bridges. This was done with all possible secrecy, but high up on Lookout Mountain the signal corps of Bragg's army, with their field-glasses, were stealthily watching, and promptly reporting every movement. The Confederates readily yielded their post at Chattanooga, but it was only to give the appearance of a retreat. In reality, they were concentrating all their forces along the banks of the Chickamauga, and already their troops outnumbered Rosecrans' by several thousands. Bragg's plan was to cross the Chickamauga at the various bridges and fords, push across Missionary Ridge to Rossville, and then, closing in upon Rosecrans' army, completely destroy it by the force of his superior numbers. Garfield, by means of his secret service system, had discovered this plan of the rebel commander, and apprized Rosecrans, who was now on the alert and confronting Bragg's troops at every feasible point of the road. "The resistance offered by the enemy's cavalry," writes the Confederate general, "as well as the difficulties arising from the bad and narrow country roads, caused unexpected delays." On the morning of the 19th of September, the battle began on the banks of the Chickamauga between Pigeon Mountain and Missionary Ridge. It raged fiercely all day, and when night closed down upon the contending armies, the contest was still undecided.