A history of the Longest March of Military in History. The Mormon Battalion was the only religious unit in United States military history in federal service, recruited solely from one religious body and having a religious title as the unit designation. In 1847, as the Mormons were in Iowa heading West, after being driven out of their homes in Nauvoo, Illinois, the U.S. Army requested 500 volunteers to assist in the Mexican-American War effort. From July 1847 to July 1848 the battalion made a grueling march of nearly 2,100 miles from Council Bluffs, Iowa, to San Diego, California...