I did say if you have a specific thing to get it in writing. If you sign a letter of intent, that is getting it in writing. Plenty of guys in my boot camp got told they could go do X job in the Navy but ended up getting a different designation during boot. This was back in the mid 2000's so it may be more standard to have the LoI but at the time plenty of us did and plenty of us didn't. And for my job, I only got to join "the nuke program" - we got to give a wishlist for which rating but it didn't mean much. I got the rating I wanted, but several guys wanted Electronics Technician and ended up as their last choice - Machinist's Mates. And I've met some decently smart infantry, but I've also met plenty of infantry that were (affectionately) window lickers. More seriously though, the ones we joked around with about being window lickers aren't actually stupid, they were just average guys, just not as quick as some of the other vets in the group (the Marine vet embraced the crayon eating jokes). I'm sure they were fine at their job though, and they followed orders well which is probably the most important thing in a soldier or sailor.