Clinton was clear; If you develop a nuke and use it to attack an ally, we can destroy.

Trump has been all over the map with his threats so it's not clear if he would attack N. Korea preemptively or only after N. Korea struck first. Here's an example:

Trump (Aug. 8): "North Korea best not make any more threats to the United States. They will be met with fire and fury like the world has never seen. He has been very threatening beyond a normal state, and as I said, they will be met with fire, fury and frankly power the likes of which this world has never seen before."

For context, Trump ad libbed his comment when asked this at a press event on opioids: Any comments on the reports about North Korea's nuclear capabilities?

Let's break down Trump's message. He is vowing to destroy North Korea if it makes any more threats to the United States. Trump doesn't define what constitutes a threat but says Kin Jong Un has been very threatening already.

The lack of precision and the way in which Trump changes key elements of his stance each time he speaks create uncertainty and increases the risk that N. Korea attacks preemptively. It also provides the North Koreans even greater incentive to quickly expand its capabilities, both nuclear and conventional. Within 24 hours of Trump's comments, Un threatened to attack Guam.