How does Tim O'Brien use imagery in Going After Cacciato?

Imagery:

"But Paul Berlin had no sense of the lieutenant's sentiment. His eyes were down and he climbed the road dumbly. His steps matched his thoughts. He did not notice the heat, or the beauty of the country, or the lieutenant's raised hand. If he had noticed, he would not have understood. He was dull of mind, blunt of spirit, numb of history, and struck with wonder that he could not stop climbing the red road toward the mountains."