Warren was a Western-themed writer and was responsible for bringing to television series like "Gunsmoke," "Rawhide," and The Virginian." He was responsible for much of the casting for these TV series, coming up with unknown actor Clint Eastwood for the starring role in "Rawhide." He was a good friend of F. Scott Fitzgerald, who wrote a letter of recommendation for Warren, which resulted him going to Hollywood and getting to work on a screen treatment of Fitzgerald's "Tender Is The Night." Warren sold more than 250 articles to magazines and was a regular contributor to the Saturday Evening Post. "Valley Of The Shadow" was one of his best-selling novels, with his novel "Only The Valiant" made into a 1950 movie, starring Gregory Peck.