If North Korean leader Kim Jong Un was searching for the perfect propaganda set piece, something designed to show his people that he's a strong leader pushing inexorably for the long-delayed, long-promised prosperity they deserve, then visiting South Korean President Moon Jae-in might be providing him with a unique opportunity. Moon believes that his deep engagement with North Korea is crucial after last year's fears of war, when Washington reacted with fury to a torrent of ever-more-powerful North Korean weapons tests. He argues better ties with North Korea will help South Koreans, and the region, by settling the standoff over...