Trump has done a good job of keeping the pressure of sanctions on North Korea and getting the UN Security Council to support increasing sanctions. But the real challenge is getting North Korea to the negotiating table and cutting a deal with them on a nuclear treaty-- he will go down in history for that. A treaty that will give us the security we want in exchange for aid, and trade agreements. Also, in exchange for NK adding to that, disarming the border, we can draw down US troops, and remove the THAAD anti-missile defense in South Korea (which is opposed by South Korea, China and Russia. The treaty will also require that China and Russia pony up and taht will require some tit for tat with the US, China, NK, and Russia.