During the Chattanooga campaign, Confederates attempted to besiege the Army of the Cumberland into surrendering, but reinforcements from the Army of the Tennessee under the command of Grant, William Tecumseh Sherman, and Joseph Hooker arrived. The Confederates were driven from the city at the battles of Lookout Mountain and Missionary Ridge in November 1863. Despite Unionist sentiment in East Tennessee, Confederates held the area for most of the war. A few days after the fall of Chattanooga, Confederates led by James Longstreet unsuccessfully campaigned to take control of Knoxville by attacking Union General Ambrose Burnside's Fort Sanders. The capture of Chattanooga allowed Sherman to launch the Atlanta campaign from the city in May 1864. The last major battles in the state came when Army of Tennessee regiments under John Bell Hood invaded Middle Tennessee in the fall of 1864 in an effort to draw Sherman back. They were checked by John Schofield at Franklin in November and completely dispersed by George Thomas at Nashville in December. On April 27, 1865, the worst maritime disaster in American history occurred when the "Sultana" steamboat, which was transporting freed Union prisoners, exploded in the Mississippi River north of Memphis, killing 1,168 people.