In the early chapters of As It Was, Cater describes his youthful experiences, including his family life, education, hunting, and other pleasant pastimes, plantation activities and relationships with slaves, as well as social conditions. These chapters are valuable for their honest views of life in the late antebellum northwestern Louisiana and northeastern Texas.

In early May 1861 a wealthy Rusk County planter, Richard H. Cumby, began recruiting a company of volunteers to serve as cavalrymen. More than one hundred men, including Douglas John Cater, answered the call. Representing the cream of Rusk County's young male population, they would be designated as Company B of Col. Elkanah Greer's Third Texas Cavalry, formed the following month in Dallas. Cater served with the Third Texas Cavalry in the Battle of Wilson's Creek and Elkhorn Tavern.

In June 1862, Douglas Cater transferred to the Nineteenth Louisiana Infantry to be with his brother Rufus, and remained with that unit until the end of the war. He participated in the Battles of Chickamauga, Missionary Ridge, Franklin, and Nashville.