Kirby;
Joel Dennis and his brother John H. ran afoul of the Provost Marshall in Bollinger county in 1863 and spent time in St. Louis afterwards. I can't find any listing where they belonged to an organized military unit with records....
The actual PM papers could be elucidating. Interesting info on Jeff Thompson's actions as well. That list of his would be quite a "Pearl Harbor File" in its day.
John R.