At the outset of the American Civil War, [the writer Ambrose] Bierce enlisted in the Union Army's 9th Indiana Infantry Regiment....In February 1862 he was commissioned First Lieutenant, and served on the staff of General William Babcock Hazen as a topographical engineer, making maps of likely battlefields. Bierce fought at the Battle of Shiloh (April 1862), a terrifying experience that became a source for several later short stories and the memoir, "What I Saw of Shiloh". In June 1864, he sustained a serious head wound at the Battle of Kennesaw Mountain, and spent the rest of the summer on...