It's beautiful, and those are wonderful pictures.
I was wondering about Cavalry in WWII... - then I saw your pictures, and realised that he was meant he was in a mounted regiment. Ignorant as I am of the US army, do you have many mounted regiments?
As to the saddle, if the tree and flocking are in good condition (and only a saddler can tell you this), then with some love and leather cream it should go on for ever. I hope it fits your horse