How the heck is getting captured a heroic act? Most nations treat their captured service members as if they were in a state of limbo...all pay and in grade promotions stop, etc.
McCain AFAICT was neither liked nor respected by his fellow POWs. I suspect that McCain acted as a POW in the same manner he now acts as a Republican (sic).
From what I read, McCain did NOT get a promotion during his captivity. Read the article I posted twice on this thread.