National Geographic : 1941 Jul
Acme At Fort Oglethorpe, Georgia, the 6th Cavalry Loads Its Mounts into Horse-carrying Trucks, or Portees Time was when all cannon, escort wagons, caissons, etc., were drawn by horses or mules. Now the army horse rides incomfort, along with the troopers, and arrives rested and fresh. Primary purpose of the portee is to transport cavalry speedily, over good roads, to rough country which trucks cannot negotiate, but where cavalry may reconnoiter. Sometimes green horses balk, throwing themselves wildly about the gangplank. Once aboard, however, they soon quiet down (page 23).