As his wife, Susie, followed the news from Collinsville, Illinois, Kelso marched in the 1862 campaign led by General Samuel Curtis’s 12,000-man Army of the Southwest, chasing the Confederate army out of Missouri and into Arkansas. After the Union victory at the Battle of Pea Ridge, Kelso joined the 14th Missouri State Cavalry as a first lieutenant. His first major battle with that regiment was an embarrassing defeat at the Battle of Neosho. Kelso’s account of the battle is vastly different from that of his bumbling colonel, John M. Richardson. Throughout, he wrote letters to Susie, hoping she would admire his courage and sacrifice and fearing that she was being seduced by a former friend.