PANMUNJOM, Korea (AP) — "Ok, let's do it."

With those words, a deliberate step and a pat on the arm of Kim Jong Un, President Donald Trump became the first sitting American leader to step into North Korea on Sunday as the two made history at the heavily fortified Demilitarized Zone. The made-for-television moment was unthinkable just two years ago, when the men were trading base insults and grim threats.

Trump's three-hour stop at the DMZ — of which about 80 minutes were spent with Kim — was a display of handshake-diplomacy for the history books, but also a chaotic spectacle reflective of the...