What is the central theme and the author’s purpose in this

What is the central theme and the author’s purpose in this text? How does the author develop and communicate this theme and purpose? Give specific evidence from the text to support your answer. (10 points).
There’s a condition in combat that occurs when a soldier is completely stressed out and is “on the verge of a nervous collapse.” In World War I it was called “shell shock.” Simple, honest, direct language. Two syllables. Shell shock. It almost sounds like the guns themselves . . .
. . . [I]n World War II the same combat condition was called “battle fatigue.” Four syllables now; takes a little longer to say. Doesn’t seem to hurt as much . . .