(Richard Grevers dramatic@xtra.co.nz):
Well, in the page that prompted this: [[Marine Corps Memorial Statue]] I was wanting to expand the abbreviations Sgt. Cpl. and Pfc. The latter occured in front of four names, and I don't think we'd want to see "Private, First class" written in full four times. I don't think we'll have an article on it any-time soon, either. Also, does anyone know what PhM. expands to as a U.S. Naval rank?
If they're used a lot, then it's probably OK to abbreviate and link the first one of each to an article about military ranks in general (which hopefully someone will notice is empty and fill in).
"PhM" isn't so much a rank as a job title: Pharmacist's Mate. That's someone who works in the sickbay of a ship.