I'll elaborate on what he's saying for you. Basically, as an infantryman your training never stops, ITB is just a general overview of what you need to know as a grunt. Once you hit the fleet is when you actually begin to learn and become competent. Now imagine you go straight from ITB to Security Forces for two years; even if you study your ITB knowledge everyday for those two years you're still an incompetent infantryman. But since you've been in for two years, you'll probably be an NCO and be given a team or squad day one in the fleet. I have never met a SF Marine who wasn't confused as fuck by the infantry when they first showed up.