How does David McCullough use imagery in Truman?

Imagery:

"Nearly all were farmers, plain-mannered and plainspoken, people with little formal education. Many of them were unlettered, even illiterate. They were not, however, poor or downtrodden." Part 1, Chapter 1, page 15

"For years afterward at reunions in Kansas City, with whiskey flowing, there would be much lighthearted banter and kidding over this first encounter with the enemy, and Battery D's so-called "Battle of Who Run." But there was nothing the least comical about the situation at the time. With his blistering verbal barrage and the vivid example of his own fierce courage under fire, Captain Truman succeeded finally in getting things in control." Part 1, Chapter 4, Page 122