Caswell Hall Barnhill enlisted in the 5th Arkansas Infantry at Pocahontas, Arkansas on November 10, 1861. He was assigned to Company H and was sent to Pittman's Ferry on the Current River for training and then on to Greenville, Missouri. He is known to have been at Corinth, Mississippi during the battle of Shiloh and probably participated in the later defense of that place. He fought with his unit across the South until captured at Paint Rock, Alabama on August 23, 1863. He was sent to Louisville, Kentucky for processing as a prisoner of war. Caswell was given the choice of joining the Federal Army or spending the rest of the war at Rock Island Prison in Illinois. Wisely he choice to "galvanize", at least temporarily.

He was assigned to Independent Battery C of Kentucky Artillery (Union) on February 24, 1864. He was promised a bounty of three hundred dollars, of which thirteen were paid. He listed his occupation as wagon-maker. He was paid a further sixty dollars of his bounty on March 24, 1864. On April 18, 1864 he was granted a 20 day furlough. He promptly made his way back to Confederate lines, purchased a horse with his Union bounty money, and joined Company E, Davies' Battalion, Arkansas Cavalry (Confederate). Embarrassed Union officers at first listed him as deserted, and then changed his listing to killed in action in order to get him off of their rolls.

He fought with the Arkansas Cavalry for almost one year until his recapture at Mound City, Kansas. He was sent immediately to Rock Island Prison where he spent the rest of the war. An old family story says that while at the prison, he made contact with a jailer who was a fellow Mason and imposed on him to allow in items sent from his family. He was paroled on May 25, 1865.

Caswell returned home to Greene County, Arkansas. He went back to his work as farmer, carpenter, mechanic, timberman, wagon-maker, and businessman. He had three more daughters and four more sons after the war. He died July 2, 1879 in Paragould, Arkansas and is buried at Pruit's Chapel Cemetery.

Caswell, like most of his brother Confederates, survived four years of war and privation by his skill and wit alone. His devotion to the cause he believed in is witnessed by his efforts to rejoin the Confederate Army after his escape. After three years of endless fighting and being captured, he risked his life by returning to fight for the South, knowing that if captured again he could be executed as a Union deserter.