The letters have to instruct the commander to retaliate in order for nuclear deterrance to work - or at least your adversary has to believe that that is what th

The letters have to instruct the commander to retaliate in order for nuclear deterrance to work - or at least your adversary has to believe that that is what the letters say. Otherwise your deterrance loses it's power. Yet if commanders get to the point of actually reading the letters, then deterrance has obviously failed. That's what makes these letters so interesting IMO.