On first read, I was wondering why on earth did they not use a train? I looked it up and found this from a primary source:

> The principal objectives of the expedition were to servicetest the special-purpose vehicles developed for use in the first World War, not all gf which were available in time for §uch U§e; and to determine by actual experience the possibility and the problems involved in moving an army across the continent, assuming that railroad facilities, bridges, tunnels, etc. had been damaged or destroyed by agents of an Asiatic enemy.

which makes a lot of sense. great reading: https://www.eisenhowerlibrary.gov/sites/default/files/resear...