Chattanooga, using Corinth as his base of supply. Buell had wished that the base for the advance upon Chattanooga should be transferred to Nashville, in the centre of Tennessee, in which case the line of railway communication would have been shorter and also less exposed to raids by the Southern cavalry. After Halleck had gone, Buell obtained permission to effect this change of base. The whole month of June had been wasted in repairing the railway with a view to Halleck's faulty plan. When Buell himself was allowed to proceed on his own lines and was approaching Chattanooga, his communications with Nashville were twice, in the middle of July and in the middle of August, cut by Confederate cavalry raids, which did such serious damage as to impose great delay upon him. In the end of August and beginning of September Kirby Smith, whose army had been strengthened by troops transferred from Beauregard, crossed the mountains from East Tennessee by passes some distance northeast of Chattanooga, and invaded Kentucky, sending detachments to threaten Louisville on the Indiana border of Kentucky and Cincinnati in Ohio. It was necessary for Buell to retreat, when, after a week or more of uncertainty, it became clear that Kirby Smith's main force was committed to this invasion. Meanwhile General Bragg, who, owing to the illness of Beauregard, had succeeded to his command, left part of his force to hold Grant in check, marched with the remainder to support Kirby Smith, and succeeded in placing himself between Buell's army and Louisville, to protect which from Kirby Smith had become Buell's first object. It seems that Bragg, who could easily have been reinforced by Kirby Smith, had now an opportunity of fighting Buell with great advantage. But the Confederate generals, who mistakenly believed that Kentucky was at heart with them, saw an imaginary political gain in occupying Frankfort, the State capital, and formally setting up a new State Government there. Bragg therefore marched on to join Kirby Smith at Frankfort, which was well to the east of Buell's line of retreat, and Buell was able to reach Louisville unopposed by September 25.