On a strategic level, Pyongyang hopes that these kinds of tests get Japan and South Korea to question the utility of their respective alliances with the United States. North Korea made clear it undertook this launch because Washington ignored its previous overture—yes, the Guam saga was actually an invitation to negotiations—and carried on with the Ulchi-Freedom Guardian exercise with South Korea.
Pyongyang didn’t mention Japan’s recent military drills with the United States, curiously enough. The implication was clear anyway: Tokyo is facing adverse security outcomes because of activities the United States is carrying out with South Korea. North Korea’s new long-range missiles allow it to make the stakes very real for Japan, and it may hope to drive a wedge between it and the United States.
In this case, the technology and strategy work together to rattle America’s allies’ confidence in Washington’s security commitments in Northeast Asia—the cornerstone of what Pyongyang calls its “hostile policy” in East Asia. This is precisely why U.S. Secretary of State Rex Tillerson released a rare readout of a post-launch phone call with his South Korean and Japanese counterparts, emphasizing that the alliances remained “ironclad” despite North Korean provocations.
What will be difficult for the United States, Japan, and South Korea to accept, however, is that Kim Jong Un will likely get away with continued launches over Japan. Missile defense, while enticing, is at best imperfect, with the costs of a swing-and-a-miss potentially too great. Sanctions—the default answer to new and greater provocations from Pyongyang—have failed to stall Kim. He introduced his current generation of long-range missiles based on advanced composite materials and, most likely, engines manufactured at home despite an extensive international sanctions regime. (China’s imperfect implementation and enforcement of existing sanctions is unlikely to change anytime soon.)
What choices does that leave? Well, there is the military option—part of what's currently “on the table,” as several U.S. officials, including most recently President Donald J. Trump, remind us. Based on the capabilities North Korea has already demonstrated, however, the risks of preemptive military action against Kim Jong Un are unacceptably high. (Again: that’s why Kim has his nukes in the first place.)
With none of these options providing a compelling way out, North Korea will continue testing its missiles—seeking to credibly demonstrate that it deters the United States. Its state media described this week's launch as a “prelude to containing Guam.” With each launch, Pyongyang, however, has left a way out: it wants to talk to the United States.
As difficult as it is for Washington to acknowledge the reality of North Korea’s capabilities, Kim knows that it's precisely his new nuclear-tipped missiles that give him the ability to bargain coercively with mighty America. Just recently, Tillerson and U.S. Defense Secretary James Mattis modified Washington’s precondition for talks with North Korea from a bona fide gesture toward denuclearization—now an outmoded pipe dream—to just “the immediate cessation” of its weapons tests.