Lincoln promoted Grant to major general and assigned him command of the newly formed Division of the Mississippi on October 16, 1863, including command of the Armies of the Ohio, Tennessee, and Cumberland. After the Battle of Chickamauga, the Army of the Cumberland retreated into Chattanooga where they became trapped. Grant arrived in Chattanooga on horseback, assisted by Major General Joseph Hooker, with plans to resupply the city and break the siege. Union forces captured Brown's Ferry and opened a supply line to Bridgeport.