I don’t think he meant to say this. Look how he tries to change the subject. I think he said it because he is considering hitting North Korea, and is likely to do so.
Not that it hurts to put some fear into Kim Jong-Un, who has been noticeably quiet lately.
As I’ve written, Trump has not done enough to go after China, which can rein in North Korea. China won’t take action against North Korea, it has to be coerced, but we’re either unwilling – because of the economic cost – or afraid to do it. It’s not clear that this would work, but it is not fully being tried.
And so we are left with war, since we cannot last in a world where Kim Jong-Un can blow up our cities.