Roy, if your ancestors were Tennessee Unionists you might check web sites for Camp Nelson, Camp Wildcat, and other refugee camps pimarily in Kentucky but in Ohio and Indiana as well. He could have easily recruited into any of the 56 Tennessee Union Regt's but it was not uncommon for the refugees to be enlisted in border states units especially if they had yankee kin folks in those regt's I did not find Byrn in any of my rosters but my collection is far from complete.