The ones who are deployed are usually the more mentally fit. They don't let random kids go on the frontlines. But the issue after enlistment/deployment is a big issue, but seperate from recruitment and the usual barracks life. If you go into the military right now, there is almost no chance you'll be stationed somewhere that is volitate. In the case of the US, you would most likely be stationed within contenential America. Maybe after a year or so you might go to a safer place like Japan or Korea, or Germany even.

The soliders who are deployed in Africa and the Middle East have to go through extensive vetting processes to be there.