What American author served in the Civil War?

Many American authors served in the civil war, but perhaps among the most famous is Mark Twain, aka Samuel Clemens. http://classiclit.about.com/library/bl-etexts/mtwain/bl-mtwain-mymil.htm http://classiclit.about.com/library/bl-etexts/mtwain/bl-mtwain-war.htm