In uk.railway Clive Coleman. twisted the electrons to say:
I watched a programme years ago on a channel like National Geographical,
and if I remember, the sub had to be in contact (radio wise) with the
white house and unless they entered the right code into the system, it
won't work. Things might have changed, but I somehow doubt it.

So if the USSR had done a depressed trajectory shot onto the White House
(or more probably Cheyenne Mountain) from just off the USA's coast as
their opening move then the entire western nuclear arsenel is unworkable?
Doesn't sound too sensible to me.

People are always claiming that the UK Tridents can't be fired without
the USA authorisation (or even that only the USA controls them), but they
never seem to be able to provide any evidence for this (or any evidence
as to why the UK would be foolish enough to sign up to such a deal).
--
These opinions might not even be mine ...
Let alone connected with my employer ...