As you know the 2nd, 3rd and 4th KY Infantry formed in Tennessee at Camps Boone and Burnett and moved through Russellville on their way to Bowling Green in September, 1861.
As the Army of Central KY was formed in BG that month, over time a force was sent to cover Clarksville and had troops at both Russellville and Hopkinsville. Many of these troops would be sent to Ft. Donelson in early February, 1862.
Of course there were also Federal forces that held Russellville. Col. Sanders Bruce's large brigade moved from there to Clarksville in December, 1862.
Greg Biggs