He has thought quite a bit about the topic. Really.

What Uncle John Taught Trump About Fire and Fury

When the president reflects on nuclear weapons, he likes to remind listeners that he's the nephew of an MIT physicist....Facebook

President Donald Trump returned this week to a recurring and favorite theme of his over the years: nuclear war and annihilation.....Amid the president's threats to unleash "fire and fury" upon North Korea if the country's nuclear ambitions continue to expand, look no further than Trump's late uncle, John Trump, for a window onto POTUS's thinking.

https://www.bloomberg.com/view/articles/2017-08-09/uncle-john-taught-trump-about-fire-and-fury