"Lt. Clemens reflects" a book review in the Jan. 13th Lexington Herald-Leader by Marshall Myers.
Mark Twain's Confederate service amounted to two weeks, but he wrote a lot about it in later years. "Mark Twain's Civil War" edited by David Rachet says that he joined a small band of rowdy and undisciplined Missourians and "we couldn't tell which side we were on."
He had answered the call of Missouri Governor Claiburne F. Jackson to "drive all invaders from her soil, not necessarily to support the South in its quest for independence."
Twain's account of his two week service is detailed in his "The Private History of a Campaign That Failed." He then joined his brother Orion who had been appointed secretary to the territorial governor of Nevada.
What Would Huck say? --Old B-Runner