=482. Battle of Murfreesborough, or Stone River.=—After securing his stores at Chattanooga, Bragg moved northwestward and erected strong works at Murfreesborough. Major General William S. Rosecrans,[213] who had now superseded Buell, advanced from Nashville with the purpose of dislodging his opponent. The armies met in a great battle on Stone River, a shallow stream which flowed between the armies, near Murfreesborough. During the first day, December 31, the Unionists were driven back, but during the second and third days, they recovered their ground. On the night of January 2, 1863, the Confederates were obliged to withdraw from the field, but the Unionists were too much crippled to follow. The battle was a costly one to both sides, the Union loss having been about thirteen thousand, and the Confederate about ten thousand. Both armies soon went into winter quarters. The battle left the control of central Tennessee in the hands of the Unionists. =483. Results in the West.=—The results of the campaigns in the West were highly encouraging to the North. The Union forces had kept possession of Missouri and had got control of the larger part of Tennessee and of the Mississippi River as far south as Vicksburg. The Confederates still had the advantage of being strongly intrenched at Chattanooga, the point in eastern Tennessee through which the railroads pass from Virginia to the Southwestern states. The armies had fought with equal bravery, but the balance of success was on the side of the North. [Illustration: CONFEDERATE RAM.] THE WORK OF THE NAVY. =484. Ironclads.=—In the East, the war was prosecuted, during 1862, partly by the navy and partly by the army. Before the outbreak of hostilities, ironclad vessels had played practically no part in naval warfare anywhere in the world. Experiments in protecting vessels with iron had, indeed, been made by the British and the French, but without much success. In the latter part of 1861, however, an event occurred which effected a complete revolution in the construction of war ships. The Confederates had secured at Norfolk the abandoned and partly destroyed frigate _Merrimac_. They decided to cut off the top of the vessel and build upon it a sort of Mansard roof so heavily plated with iron and so sloping that it could throw off the heaviest cannon shot. They also fitted up the ship with an iron prow, or beak, put in powerful engines, and filled the space within the roof with heavy guns. At about the same time, Brigadier General A. W. Ellet, an engineer in the Union army, devised and built in the West a fleet of steam rams of similar construction, which did great execution at the battle of Memphis. [Illustration: NORFOLK, HAMPTON ROADS]