Let me offer an unconventional opinion of the recent developments surrounding diplomacy around North Korea's nuclear program.
I see this process as basically one of North Korea conceding to international pressure -- especially from China, their main trading partner, who did in fact cripple North Korean exports last year under elevated pressure to do so from us -- to disarm themselves of their most important deterrent: their nuclear one. If we consider that a desirable goal, then yes, Trump deserves the principal credit because this is basically North Korea conceding to indirect American pressure on that front. However, I don't consider this a desirable goal. We have seen our government play this game with regimes they don't like before enough times now to know what the outcome will realistically be. For example...
-In Iraq, we first supplied Saddam Hussein's police state with various weapons of mass destruction and didn't bat an eye when he used them against Iranian civilians in huge numbers. But after he threatened our access to Middle Eastern oil supplies by invading Kuwait, we turned against his regime, forcibly expelled it from Kuwait, and demanded that Saddam disarm himself of those weapons. We then accused him of failing to follow through with said disarmament in order to compel an investigation by UN weapons inspectors. Once it became apparent that Saddam's regime had, in fact, disarmed itself of WMDs, we decided that it was safe to invade and replace the regime with one more to our liking. And the world still endures the consequences to this day.
-In Libya, we demanded that Muammar Gaddafi disarm his regime of WMDs in the early 2000s as well, around the same time frame that we invaded Iraq, in order to create a similar situation. Once the regime was fully disarmed of said weaponry and a rebellion broke out, we aided it by bombing the regime out of existence in 2011.
Around the same time frame that we were demanding that UN weapons inspectors investigate the situations in Iraq and that in Libya, we (under the George W. Bush government) also demanded a similar UN investigation into whether North Korea had a secret nuclear weapons program that was still operating. The difference was that they responded by confirming that they did, in fact, have such a program and had no intention of giving it up. This last regime is still around. You do the math on that. Is the American-led demand that Second World police states disarm themselves of WMDs in fact about making the world a less dangerous place...or is it about making those countries safe to blow up so that we can replace their governments with ones we like better?
Take notice of the fact that Trump will be pulling us out of our nuclear deal with Iran, which Iran has not violated in any way, practically on the same day that he'll be meeting with Kim Jong Un to negotiate the elimination of his country's nuclear deterrent. The fact that these two developments will be taking place simultaneously shows the cynicism with which our government will be approaching any deal it may reach with North Korea's.