PANMUNJOM, Korea—U.S. Defense Secretary Ash Carter appeared in the demilitarized zone between North and South Korea to assure Seoul that the U.S. stands ready to help defend it against any aggression from the North.
“Our alliance with South Korea is ironclad and strong,” Mr. Carter said, as North Korean soldiers watched intently from just across the border area. “Deterrence is guaranteed through strength.”
Mr. Carter, on a...