"Logically depend" has an easy interpretation: the second move must be also be valid if performed before the first move. [You could do a harder variant where both moves must be legal simultaneously.]
This is a complete misunderstanding of US nuclear policy and weapons systems. It's designed to enable the president to launch missiles at any target as rapidly as possible, not to doublecheck or safeguard against him.
You might say "sure, but there are people who have to actually execute those orders." But give the Pentagon some credit--those are people who have been systematically selected because they follow orders quickly and without question. For example, consider what happened to Harold Hering when it became obvious that he was not one of those people.