Before and during WWII they were probably more integrated into the Navy and really were not a part of anything like the Joint Chiefs of Staff until a time after that (mid 70's). I would now call them very nearly an independent service.Mikey wrote:They do have their own materiel, ranks, and field command; but they are part of the navy as far as general staff, etc.
I agree with the vote that Security is a different job, almost like MP's or something.
That being said I will quote Admiral Porter during the civil war.
"A ship without Marines is like a garment without buttons."
Simply put, no organization that draws its heritage so heavily from the United States Navy and the Royal Navy would ever, ever put ships in service without Marines. Starfleet badly needs Marines because such people were even more valuable in the 1600-1800's when ships were not where they could just call up amphibious troops one a week or two's notice. But that is another discussion.