This is the most egregious crime against humanity possible. Not only will it kill and destroy millions (if not billions) of human beings but it will destroy the earth land, plant life and animals. It also will damage and destroy the atmosphere. There will be no place on the surface of the earth that is livable. Just ask the people of Hiroshima and Nagasake:

https://www.nationalww2museum.org/war/articles/atomic-bomb-hiroshima

Any nation or government contemplating such an act is beyond evil. They have no regard for our planet, our galaxy or our human race. The only power to protect us from such an act is the awesome POWER OF GOD. The best defense is PRAY WITHOUT CEASING that the earth will be spared from this total annihilation.