History is made as Kim Jong-un crosses the border. It’s the first time a North Korean leader has set foot in the South. This step is the latest chapter in Kim’s head-spinning makeover from a stern-faced despot into a smiling diplomat. Somebody President Trump ridiculed as “Little Rocket Man” — “Rocket Man is on a suicide mission for himself” — has suddenly become “very honorable.” “He really has been very open, very honorable.” Here is how Kim did it. Kim may have felt that he had the leverage to turn a diplomatic corner once he was able to show that his country could be a nuclear power. Kim kicks off his charm offensive by dispatching his so-called army of beauties to the Winter Olympics in Pyeongchang. He also sends his sister Kim Yo-jong — the first time a member of the Kim family visited South Korea since the Korean War. She becomes an overnight sensation in the South. Kim hosts a delegation of high-level South Korean officials in Pyongyang. The officials from the South deliver a bombshell to the White House: Kim wants to meet Trump, and Trump, shocking the world, says yes. “Trump responded saying yes.” “Surprise, praise, skepticism.” “This was indeed a shocker.” Kim secretly leaves the country for the first time since taking power. His destination: Beijing, where he visits with Chinese President Xi Jinping. It’s Kim’s first meeting with another head of state. Kim hosts the International Olympic Committee in Pyongyang to thank them for their support and to say that North Korea will take part in the Tokyo and Beijing Olympics. Kim loosens North Korea’s iron grip on pop culture as he and his wife rock out at a two-hour K-pop concert in Pyongyang. He even poses for a photo with a popular South Korean girl band, Red Velvet. Kim secretly meets and has a photo op with then-C.I.A. director Mike Pompeo, signaling planning is underway for a summit. North Korea announces a new pledge to end nuclear and missile testing and close a nuclear test site. Kim takes his historic stroll and calls for an age of peace. It may mark the beginning of a historic thaw. Whatever happens, it’s clearly the start of a new Kim Jong-un.