Once a Warrior King: Memories of an Officer in Vietnam by David Donovan.

A very insightful book on the dynamics of small unit leadership, especially in the context of a small advisory unit that is isolated from main body U.S. forces. I found the anecdotes on cultural understanding and engagement very helpful as I prepared for my MiTT mission a couple of years ago. While the advisory mission has changed somewhat in the last year, the ideas on building and nuturing relationships with your counterpart without "going native" are still worth a read.