upon president lincoln's call for volunteers at the outbreak of the civil war, atkins immediately chose to defend the union cause and entered the volunteer ranks of his home state. he served in the western theater of the conflict. he was appointed a captain in the 11th illinois infantry on april 30, 1861, and was promoted to major on march 21, 1862. by april he was assistant adjutant general of the 4th division in the army of the tennessee, but resigned on april 17 to take a two-month respite from duty for health reasons.