We do know some one in US put a lot of effort, esp. was behind sending three aircraft carriers into the region. Has done enough posturing but had incredibly held back so the situation does not escalate and talked with Chinese to impose and/or stick with sanctions. I do not know who it was, its most likely a huge team of people. All this happened after the State department was purged of his high level officials.

What I know is this, there is a huge team of American civilian and military that worked hard to tackle the DPRK problem and have achieved or at least partially achieved their objective. At the very top level these men and women are lead by one guy, Donald J Trump.