Originally Posted by ju-on

They accept you as is, because they know you've already had training well beyond the scope of what theirs is.

But if anyone from another branch decides they want to move into the Marines. It doesn't matter how high of rank they had, they will lose their rank and go back to the bottom of the gene pool and become "Recruit" once again, and go through all Marine boot camp just like any other marine has to. The title marine isn't given away, it's earned, no way around it.

Originally Posted by ju-on

Because once you've gone through Marine boot camp, you never have to go through another branches boot camp if you ever decide to move to another branch. They accept you as is, because they know you've already had training well beyond the scope of what theirs is.