On Sunday in the “Peace Village” of Panmunjom in the Demilitarized Zone, President Donald Trump stepped over the Military Demarcation Line and took twenty steps into North Korea with Kim Jong-un, the dictator of the Hermit Kingdom. The pair immediately walked back another twenty into the South, where they met for fifty minutes.The brief visit by the president of the United States of America to the Democratic People’s Republic of Korea delighted Kim, who smiled broadly and constantly. Almost certainly, the forty-step outing alarmed Xi Jinping, the Chinese ruler, who was not in attendance.Trump is now the first sitting American leader to go to North Korea. Yet that was not the important element of Sunday’s events. In all probability, he planned those activities to both rile Chinese leaders and upend relations in North Asia.The American president on Saturday, just before his much-anticipated meeting with Xi in Osaka at the G20, tweeted about the possibility of his meeting Kim in the DMZ. The timing of the tweet is unlikely to have been a coincidence. There was speculation that at his meeting with Trump, Xi was going to offer cooperation on North Korea as a means of obtaining concessions on other issues. That is surely why Xi’s first trip to North Korea took place in June, just before the G20. Beijing and Washington, of course, are locked in what most observers term a “trade war,” the primary topic of conversation at the Trump-Xi meet in Osaka. With the tweet, however, Trump seemed to be saying to his Chinese counterpart that he did not need Beijing’s help on North Korea.