When only one country had them. After the Soviets got one, nuclear war became uwinnable.
Look how many countries have them since. And it doesn’t matter how many you have, if you have enough to destroy the other guy. Whoever now shoots first dies as surely as those who shoot last. 30 minutes its over.
The value of having nukes is the other guy knows he will pay a horrific price.
Hence the value of reminders.