Screenwriter Frank S. Nugent developed the concept for the film while writing the screenplay for "She Wore a Yellow Ribbon" in 1948. During research, Nugent consulted historians Dee Brown and Martin F. Schmitt, authors of "Fighting Indians of the West", for sources of information about the use of "Galvanized Yankees", and learned that Confederate plans to connect El Paso, Texas with California were formulated in late 1864. He submitted his story, "The Yankee From Georgia", to Metro-Goldwyn-Mayer but did not receive an offer. The project for Fox began with the working title, "Trumpet to the Morn". The circumstances of the recruiting and delivery of Tucker's men are similar to those experienced by Union Capt. Henry Palmer and Company K of the 11th Ohio Cavalry from Camp Chase, Ohio, to Fort Kearney, Nebraska, and thence on to Fort Laramie, Wyoming in 1864. They were also the only former Confederate cavalrymen (originally part of Morgan's Raiders) to see service as "Galvanized Yankees" on the Western frontier.