There have been two monumental policy failures in a row vis-à-vis North Korea, first the Sunshine Policy and then the Six Party Talks.
The Sunshine Policy was created in 1998 by South Korean President Kim Dae-jung after at least three million North Koreans starved to death due to gross incompetence on the part of Kim Jong-il. The collapse of the Soviet Union resulted in drastically reduced aid reaching the DPRK, but emergencies define leaders, with superior ones rising above the fray. The South Korean Kim threw the North Korean Kim a lifeline, agreeing to give massive amounts of aid without conditions. Not surprisingly, Kim Jong-il used most of that aid for weapons development. The Sunshine Policy continued through the term of Kim Dae-jung's successor, Roh Moo-hyun, but it practically ended in 2006 with the first North Korean nuclear test.
South Korea should have demanded some concessions, not least that it be allowed to distribute all aid directly to the people who desperately needed it, but it gave all aid to the DPRK which used it mainly to feed the military and continue weapons research. The other concession should have been an emptying of the labor camps.
The Six Party Talks started in 2003, but stalled after the DPRK started testing nuclear devices in 2006, with North Korea walking out of negotiations in 2009. Then in early 2012, Kim Jong-un announced that it was suspending nuclear tests and would allow international inspectors to inspect its facilities.
It's not at all coincidental that the DPRK conducted nuclear tests in October 2006, May 2009, February 2013, January 2016, and September 2016, not to mention the flurry of missile launches starting in 2016. The DPRK played the international community like a violin.
North Korea only needs a few more years of missile tests to perfect its guidance systems and then it will be able to strike anywhere in the world.
"If the ambitious testing rate continues, North Korea may have an effective nuclear-tipped inter-continental ballistic missile by the end of Trump's four-year term," noted the IISS.
This is a continuation of the policies of Kim Il-sung, who in a lifetime of lies never lost his desire to reunify the Korean peninsula and run it like one big labor camp. Kim Jong-il and Kim Jong-un have never lost sight of that ghastly vision, though the former never missed an opportunity for companionship with young females, fine wine, and imported foods.
North Korea has always been different than the DDR, the other famous totalitarian half of a country. The Soviet Union definitely had designs on Western Europe, but the DDR did not invade its other half. During the Cold War, NATO feared Soviet armor streaming in via the Fulda Gap and today NATO fears Russia could sever the Baltic States from the rest of NATO via an attack through the Suwalki Gap, but North Korea actually invaded in a surprise attack, though it teaches its citizens that the U.S. and South Korea were the ones to invade.
Kim Jong-un does not want to dominate the world, unlike China. He merely wants to complete his grandfather's dream of reunifying the Korean peninsula. His WMD antics are intended to force the U.S. out of the peninsula and coerce the ROK into reunification on his terms. He is probably not in touch with reality because of the large number of sycophants who have always surrounded the Kim family.
There is no point to more discussions with the DPRK, as every communication from it is a lie and a gambit for furthering its weapons programs. And there is no point to more discussions with China, which opposes THAAD deployment because it could be used to research China's missile radars and control systems, unless the discussions are of the arm-twisting variety.
China could pressure the DPRK into halting its weapons programs by preventing Chinese companies from supplying North Korea with missile parts, turning the valves on the pipeline which supplies oil, and inspecting far more than the current 5% of trucks traveling from China to the DPRK to turn the screws on Kim Jong-un and the elites. Contrary to popular belief, more sanctions will not bring North Korea to its knees unless China is an active participant.
The recently elected Moon Jae-in, former chief of staff for Roh Moo-hyun, the president who killed himself fifteen months after leaving office due to corruption investigations, said, "Both the Lee Myung-bak and Park Geun-hye administrations completely failed in resolving the North Korean nuclear issue," but in truth the Kim Dae-jung and Roh Moo-hyun administrations were just as bad.