https://worldview.stratfor.com/article/what-us-would-use-strike-north-korea
Already did. The question does remain, as outlined in subsequent sections of this article, as to the capability of an effective retaliation. Costly? Potentially. Millions of casualties? Not likely. Like a bully's bluff, once called, turns to meekness, so could Kim's. Yet that same unsure possibility only substantiates the necessity of preventing further nuclear capability.
Am I a warmonger? Hardly. Been there. To me, our best chance still lays with China and the UN's cooperation.