[pdonis]

actually the president can fire any cabinet officer or (almost) any non-judicial appointment at any time. The Supreme Court has agreed that the president has this authority.

Hm, yes, I see on reading about the Myers v. United States decision that, as usual, Supreme Court jurisprudence makes less sense than it ought to. :-)

I still think, though, that a JCS Chairman in the position I described would question (and would be right to question) a President who conveniently fired a SecDef who did not concur with a nuclear launch order.