My personal assessment of the situation in No. Korea is they are lying, and war is inevitable, however President Trump will continue everything possible to avoid it.
The argument against military action is that it should be a last resort. That we should try everything else first.
By going further than any other President has in terms of trying to assuage NK's fears, etc., Trump will have demonstrated that there is no solution, short of a military one, that will stop NK from fielding nuclear-armed missiles capable of hitting the U.S.. The argument that "we should try something else" will be exhausted, because Trump already will have done that.
At that point, Trump's speech on why military action is necessary will almost write itself.