President Trump can build a wall as a military training activity. In a combat area concrete walls may be needed as part of a bunker to protect personnel or supplies. A wall can protect buildings from a truck bomb on a nearby road. Thus military personnel need to know how to construct concrete walls The southwestern states provide a good location to train personnel to construct concrete walls in the Middle East because it has a relatively close match in terrain, climate and soil. Training benefits would include practice in moving personnel, equipment and supplies into an area and learning...