How does Michael Herr use imagery in Dispatches?

Example of Imagery:

"His face was all painted up for night walking now like a bad hallucination, not like the painted faces I'd seen in San Francisco only a few weeks before, the other extreme of the same theater. In the coming hours he'd stand as faceless and quiet in the jungle as a fallen tree, and God help his opposite numbers unless they had at least half a squad along, he was a good killer, one of our best".