How can nuclear weapon be good?

Answer 1

A nuclear weapon can be beneficial in that the owner countries of weapons are much less likely to attack each other. For instance, the US and Russia never directly attacked each other during the cold war, despite the incredible antagonistic bent of the two countries toward each other. The reason for this is that both countries practiced something called mutually assured destruction (MAD) this polity asserts that if one country launches missiles at the other, the attacked country will immediately start a full counterattack on the country that launched the missiles originally, ensuring the complete destruction of both countries. This may sound like a bad thing (and it is if it ever happened) this policy prevented war during the cold war.