"...all us old guys who are just jaded, not stupid."

True - I neglected to add this to the end of my line you quoted.

What shouldn't be overlooked in this discussion is that regardless of what career path one chooses in life one will experience a lifelong compromise between the inner Massengale and the inner Damon, and a lifetime of interaction with others who at various times will exhibit qualities of either if observed long enough. (They have their own inner struggle, after all.) While Once an Eagle set that conflict against a military background it could certainly have been done within a corporate or academic setting, too. The author chose that with which he was familiar, which was also a setting that would have broad appeal (in circa-1970 America) and provide action sequences.

There's an incident early in the book (Damon's pre-military life) where he knocks someone down a flight of stairs. One can read the book for a full examination of the circumstances surrounding that. But the book details a full life, and as with most fiction takes its characters along an arc wherein they are changed. Much about the book - including the length - is certainly outdated by today's standards, but due to that length it shouldn't be characterized by events in chapter one.

So, setting the book aside: Damon and Massengale are no more or less than caricatures of something that exists in part in each of us, and not unique to military life. I believe those of us in the mid-latter chapters - jaded though we may be - hope those in the earlier continue to progress with enthusiasm for the task.