instructed Sherman to attack Johnston. Sherman conducted the ensuing Jackson Expedition, which concluded successfully on July 25 with the re-capture of the city of Jackson. This helped ensure that the Mississippi River would remain in Union hands for the remainder of the war. According to Holden-Reid, Sherman finally "had cut his teeth as an army commander" with the Jackson Expedition. Chattanooga After the surrender of Vicksburg and the re-capture of Jackson, Sherman was given the rank of brigadier general in the regular army, in addition to his rank as a major general of volunteers. His family traveled from Ohio to visit him at the camp near Vicksburg. Sherman's nine-year-old son, Willie, the "Little Sergeant", died from typhoid fever contracted during the trip. Ordered to relieve the Union forces besieged in the city of Chattanooga, Tennessee, Sherman departed from Memphis on October 11, 1863, aboard a train bound for Chattanooga. When Sherman's train passed Collierville it came under attack by 3,000 Confederate cavalry and eight guns under James Ronald Chalmers. Sherman took command of the infantrymen in the local Union garrison and successfully repelled the Confederate attack. Following the defeat of the Army of the Cumberland at the Battle of Chickamauga by Confederate general Braxton Bragg's Army of Tennessee, President Lincoln re-organized the Union forces in the West as the Military Division of the Mississippi, placing it under General Grant's command. Sherman then succeeded Grant at the head of the Army of the Tennessee. At Chattanooga, Grant instructed Sherman to attack the right flank of Bragg's forces, which were entrenched along Missionary Ridge overlooking the city. On November 25, Sherman took his assigned target of Billy Goat Hill at the north end of the ridge, only to find that it was separated from the main spine by a rock-strewn ravine. When he attempted to attack the main spine at Tunnel Hill, his troops were repeatedly repelled by Patrick Cleburne's heavy division, the best unit in Bragg's army. Grant then ordered Thomas to attack at the center of the Confederate line. This frontal assault was intended as a diversion, but it unexpectedly succeeded in capturing the enemy's entrenchments and routing the Confederate Army of Tennessee, bringing the Union's Chattanooga campaign to a successful completion. After Chattanooga, Sherman led a column to relieve Union forces under Ambrose Burnside thought to be in peril at Knoxville. In February 1864, he commanded an expedition to