This is far from the first time that the two East Asian democracies have feuded over their troubled history, including Japan’s colonization of Korea from 1910 to 1945. But Mr. Trump has done much to exacerbate the latest spat, first by modeling mercantilist tactics and then by doing little or nothing to defuse the conflict.
The flare-up started with a questionable ruling by South Korea’s Supreme Court, which said Japanese firms must compensate South Koreans used as forced laborers during World War II despite a 1965 treaty settling those claims. In July, the Japanese government of Shinzo Abe, a nationalist who has worked hard to cultivate Mr. Trump, responded with a Trumpian measure: restrictions on exports to South Korea, including chemicals vital to its big chip-manufacturing industry.
The previous South Korean government, under the conservative Park Geun-hye, had tried to head off the court’s ruling after striking a deal with Mr. Abe on another sensitive subject, South Korean women forced to serve as “comfort women” for the Japanese army. But the leftist Moon Jae-in, who succeeded her, chose to play on the easily inflamed Korean resentment toward Japan. Having already dismantled the earlier deal on comfort women, he responded aggressively to the Japanese export restrictions, first announcing the cancellation of the intelligence-sharing and then conducting military exercises near islets claimed by both countries.
All this came as a blow to U.S. diplomats who had worked painstakingly to broker the intelligence deal and to encourage the settlement on comfort women. Yet, other than issuing a statement criticizing the South Korean move on intelligence sharing, the Trump administration has made little effort to repair the rift. This, even though North Korea’s recent testing of several new short-range missiles capable of striking both South Korea and Japan has made cooperation between them more urgent than ever.
President Barack Obama made it a priority to ease tensions between these vital U.S. allies, even convening a trilateral meeting with Ms. Park and Mr. Abe to break the ice between them. Mr. Trump, in contrast, has publicly complained about the expectation that he should do something. “How many things do I have to get involved in?” he whined after getting a mediation request from Mr. Moon in July. Thanks to such thinking, the U.S. strategic position in East Asia is steadily deteriorating, to the advantage of North Korea and China.