U.S. President Donald Trump took office determined to slow North Korea’s nuclear and missile programs. Since then, Pyongyang has accelerated the pace of its missile tests and has signaled its intention to flight-test an intercontinental ballistic missile (ICBM) capable of striking the continental United States. Meanwhile, Washington’s relationship with South Korea—a partnership that is essential to confronting the North’s advances—has been faltering since December, when South Korea’s former president Park Geun-hye was impeached. Over the months that followed, Trump administration officials met with Japanese and Chinese leaders. Yet South Korea lacked a head of state who could forge the kind of personal connection that other governments had developed with the U.S. president.
Real fissures have opened in the U.S.–South Korean alliance. If they are not repaired, the partnership could falter just as North Korea nears an operational nuclear capability. The June 29–30 summit between Trump and Moon Jae-in, South Korea’s new president, will offer the chance to mend the two countries’ neglected ties and develop a more effective policy toward North Korea. The outcome will help determine whether a nuclear North Korea is contained, constrained, and deterred.