Each British nuclear submarine carries a letter from the British Prime Minister. It is kept locked away in a double safe, only to be opened if there is a nuclear war.
Why is this done in an age of instant electronic communication?
This is a legacy from the cold war but is still relevant even today.
During the cold war the West was under threat of nuclear attack from Soviet forces, and indeed the opposite was true. If one side believed it could attack and not suffer retaliation from the other side then it might think it was worthwhile. If they knew that they would suffer retaliation then they would not attack as it would lead to ‘mutually assured destruction’ (also known as MAD).
The problem for the country potentially under attack is how to make the threat of retaliation a credible one. If they don’t then the attacking side might think that after the nuclear attack the other side would lose heart and have no reason to retaliate as their country would already be destroyed.
The reason that British nuclear submarines carry letters is to give them orders as to what to do in the event of nuclear war. If the submarine commander knows there is a nuclear attack then the letter will instruct them how to respond. This means that the side being attacked can guarantee retaliation from their subs as they will have to follow the orders.
This means there is now a credible threat of retaliation which stops the attack in the first place.
Today’s takeaway: Threats need to be credible to be effective. Sometimes taking away choices is an effective way to do this.