In late June 1863, Union Major General William S. Rosecrans launched a massive offensive from Murfreesboro to drive Confederate General Braxton Bragg's 43,000-man Army of Tennessee from its entrenchments at Shelbyville and Wartrace and possibly out of the state. Rosecrans planned to capture Chattanooga and, in his words, "rescue loyal East Tennessee from the hands of the Rebels." The campaign was bold and swift, with relatively few engagements, and by July 4, the 70,000-strong Union Army of the Cumberland had forced a Confederate retreat to Chattanooga, leaving nearly all of Tennessee in Union hands. To maneuver Bragg out of his Shelbyville trenches, Rosecrans divided his army into four independent columns: Major General Gordon Granger advanced south from Murfreesboro to threaten the main Confederate infantry at Shelbyville; Major General Alexander McCook moved south through Liberty Gap; Major General George Thomas marched southeast down the Manchester Pike, the main road to Chattanooga; and Major General Thomas L. Crittenden advanced east along the McMinnville Turnpike before turning south to cross the Highland Rim below Bradyville at Gillie's Gap. Rosecrans aimed to concentrate the bulk of his army at Manchester, push on to Tullahoma, and seize the road to Chattanooga before the Confederates could respond. Only rain and poor road conditions slowed the Union advance.