While it would certainly be good news to see the end of the war and end to nuclear threats, at best it is unknown what affect Trump's tough talk, threats, and sanctions had on the situation. Prior administrations certainly talked tough to N. Korea, with mixed results. Some would argue that it is only now that N. Korea's one and only nuclear facility is now in ruins due to a mountain collapsing on it, that they are coming to the table to talk peace, and that was the prime motivation. No doubt Trump will trumpet this as a victory, but as usual with something this important and historic, there were many factors at play.
http://www.bbc.com/news/world-asia-43895428
Claim: Donald Trump and South Korean President Moon Jae-in agree the US President deserves credit for peace talks with North Korea.
Verdict: Only the historical record will reveal what influenced these talks, but evidence suggests it was the South Koreans who encouraged dialogue with the North, along with pressure from Chinese enforced sanctions.