John Henry Callin was a soldier for the Union in the Civil War, serving in the 21st Battery of the Ohio Light Artillery. Two of his brothers also served: George, who would later publish the Callin Family History, served with John in the 21st, James enlisted in the 67th Regiment of the Ohio Infantry and was wounded in the charge at the Second Battle of Fort Wagner, South Carolina, 18 July 1863. (That was the battle depicted in the 1989 film, Glory.)

John recorded his experiences in a book of poems he composed during and after the war.

After his death in 1913, that book was handed down through the family to his great-granddaughter, Vicki (Callin) Hunt, and was edited for publication by Vicki and by John's great-great grandson, Tad Callin.