Fast Eater
Soldiers have trained themselves to eat meals very quickly because they usually need to get back to their post. It could also be because they are in survival mode as they are in a war zone. Never assume it will be easy for someone who has been in the military to go back to the way they ate pre-army.
Military Jargon
It’s highly likely you’ve heard expressions like “affirmative”, “negative” or “roger that” in computer games and films. Actually, this is how soldiers speak, which they take with them even after they leave the service. It’s like learning a new language, and once you have learned it, letting it go becomes hard to do.