In 1863 a two-book set titled "Battle-Fields of the South, from Bull Run to Fredericksburg . . . " was published in London. The author identified himself as "An English Combatant" and gives the clue that his initials are T.E.C. clues in the books indicate the 'T' was for Tom/Thomas. He started as an enlisted man in a Mississippi company from (apparently) Yazoo City, but by the time the book came out he was a "Lieutenant of Artillery on the Field Staff."
Though his stories are about the war in Virginia, he publishes letters from a friend fighting much further west (Kentucky, Tennessee).
Who was "T.E.C." and what was his original Mississippi regiment?
p.s. to get a view of volume I you must Google "Battle-feilds of the south", volume II isn't mis-spelled.