For two monthsfollowing the Battle of Chattanooga, the Confederates had kept the Union army bottled up inside a tight semicircle around Chattanooga. When Grant arrived in October, however, he immediately reversed the defensive posture of his army. After opening a supply line by driving the Confederates away from the Tennessee River in late October, Grant prepared for a major offensive in late November. It was launched on November 23 whenhe sent General George Thomas to probe the center of the Confederate line. This simple plan turned into a complete victory, and the Rebels retreated higher up Missionary Ridge. On November 24, the Yankees captured Lookout Mountain on the extreme right of the Union lines, and this set the stage for the Battle of Missionary Ridge.
The attack took place in three parts. On the Union left, General William T. Sherman attacked troops under Patrick Cleburne at Tunnel Hill, an extension of Missionary Ridge. In difficult fighting, Cleburne managed to hold the hill. On the other end of the Union lines, General Joseph Hooker was advancing slowly from Lookout Mountain, and his force had little impact on the battle. It was at the center that the Union achieved its greatest success. The soldiers on both sides received confusing orders. Some Union troops thought they were only supposed to take the rifle pits at the base of the ridge, while others understood that they were to advance to the top. Some of the Confederates heard that they were to hold the pits, while others thought they were to retreat to the top of Missionary Ridge. Furthermore, poor placement of Confederate trenches on the top of the ridge made it difficult to fire at the advancing Union troops without hitting their own men, who were retreating from the rifle pits. The result was that the attack on the Confederate center turned into a major Union victory. After the center collapsed, the Confederate troops retreated on November 26, and Bragg pulled his troops away from Chattanooga. He resigned shortly thereafter, having lost the confidence of his army.
The Confederates suffered some 6,600 men killed, wounded, and missing, and the Union lost around 5,800. Grant missed an opportunity to destroy the Confederate army when he chose not to pursue the retreating Rebels, but Chattanooga was secured. Sherman resumed the attack in the spring after Grant was promoted to general in chief of all Federal forces.