[roywiggins]

The entire system is designed to eliminate human nuance once the order is given. Exactly how successful it is is impossible to say, but it's designed to make carrying out the order both fast and straightforward.

The only tricky bit is if the President wanted to execute a nuclear plan that hadn't been devised yet. But if there's an existing one (attacking NK, Russia, Iran) then ordering a first strike is really straightforward with an absolute minimum of people in a position to refuse.

[hchz]

This article doesn't address important differences in the scenario in which a launch order is given out-of-the-blue, and when a launch order is issued following certain events.