To kill off a mentor/friend or not?

Okay, that makes a lot more sense now. And yeah, they'd probably be "green army" Marines, although there might be some Recon along for the ride too, but it wouldn't be a detachment, it'd be, IIRC, a Marine Expeditionary Unit (MEU), which is kind of a standard rotation thing for the grunts. Us DLI weenies, on the other hand, did everything all messed up and backwards, so standard TO&E are a complete mystery to me. At one point, our company formation consisted of fewer than twenty Marines....

 

Yeah, I was confused as well for a sec, but I assumed the rest of the sentence only made sense when he's talking about SciFi.

 

Killing the mentor is done because the protagonist has to detach himself from the animus, the aggressive father in order to reach the next stage of maturity in his journey and take command of his quest or destiny. If the mentor isn't out of the way somehow, the protagonist stays under his shadow and never needs to become a metaphorical adult. As it's assumed the mentor will know what to do.

In other words:

 

I just read "SF" as generic "Spec-Ops". SEALS, Green Berets, SAS, SBS, Spetsnaz... If I *didn't see them*, I don't think I'd ask what they were, exactly.

Buncha shitbird ammosexual lance corporals with credit cards playing hide and seek from their squad leader, prolly...

 

It's a new world, sometimes DADT is the best policy....

 

As far as if it's sci-fi - Yes. It is set in ~3400 A.D.

While issues with limbs being removed, the armor these guys wear practically is their medic. Their response time is stupendous, so battlefield casualties take a bit more than what we're used to, and after the initial shock of "OMG I just lost an arm," there is no longer the concern of "how will I live my life without an arm," it's "Dude my new arm is going to be so freaking awesome." People in this universe are known in some cultures to get limbs amputated just for the purpose of getting new, better bionic ones. (And in others, there is still vast stigma against AI and bionic body parts).

American SF are not routinely stationed on warships - which is exactly why you do know who they are. They stick out like a sore thumb.

While this is from my personal experience, it is also intended to be the experience of my MC - a lot of his experiences on his ship are that of my own on my ship.
Space-travel in this 'verse works on a "it takes months to get some places" vice weeks, and ship-travel is the fastest, vice air travel for modern era, so SF units would have to hitch-rides with ships to be able to be rapidly deployed.