South Korea can now build missiles able to reach Beijing, with US blessing

But last month, the Biden administration removed the final limits on Seoul’s missile program, abolishing what had been a roughly 500-mile cap on South Korea’s ballistic-missile range. It is a key change: Seoul’s missiles, in theory, can now fly far enough to strike Beijing, Moscow or anywhere else.

Kim Jong Un’s regime in North Korea has been expanding its nuclear arsenal, and China’s military strength has been growing. The U.S., without provoking others by moving in its own weapons, can see a close ally develop technology that strengthens its own regional military deterrence. Seoul gets back its full nonnuclear weapons sovereignty after long advocating for such a move.

Having better-armed allies will help Washington, especially in light of worsening disputes with Beijing over Taiwan and the South China Sea, and ups the ante for China to participate in North Korean diplomacy, security experts say.

“South Korea can already directly counter the North Korean missile threat," said Oh Miyeon, a director at the Atlantic Council, a think tank in Washington. “The lifting of the missile guidelines, therefore, has regional security implications, which goes beyond the Korean Peninsula."

The U.S. has enforced what are known as missile guidelines on Seoul since 1979, when South Korea was under a military dictatorship that in previous years had secretly pursued a nuclear program of its own. The original limits capped flight range at roughly 110 miles, not long enough to hit Pyongyang from the inter-Korean border. The maximum payload the missiles could carry was about half a ton, less than what Germany used during World War II.

Those restrictions didn’t change for more than two decades, until the U.S. extended the flight range to about 185 miles in 2001, then expanded it again to roughly 500 miles in 2012.

But North Korea’s spree of weapons tests in 2017 prompted the Trump administration to drop any payload limit on South Korea’s missiles. Last year, Washington let Seoul develop solid-fuel space rockets that have the potential to aid military surveillance.

Lifting the remaining cap on South Korea’s missile range had been discussed during the end of Donald Trump’s presidency, according to people familiar with the talks. But the two countries were engulfed in contentious military cost-sharing talks, fueled by Mr. Trump’s calls for Seoul to pay significantly more. Negotiations about abolishing the missile-range caps stalled.

Within weeks of President Biden taking office, having promised to restore America’s alliances, the U.S. struck a five-year agreement on the 28,500 American forces stationed in South Korea. Then, during South Korean President Moon Jae-in’s visit to the White House last month, the two countries said the U.S. would remove the final missile limits.

South Korea is likely to use the new weapons autonomy to improve the country’s military satellites, which require similar technology to that used in long-range missiles, say former South Korean military officials and security experts. The country’s efforts won’t include a nuclear pursuit, as Seoul remains a signatory to the Nuclear Nonproliferation Treaty.

“This fits into the broader competition with China and the Biden administration’s wish to approach that through more cooperation with allies," said Mason Richey, a professor at South Korea’s Hankuk University of Foreign Studies.

China hasn’t publicly protested the U.S. policy shift on South Korea’s missile program. North Korea didn’t issue a formal statement from the government, opting for a milder state-media response by publishing a column written by an international-affairs critic. The U.S. move to drop the missile restrictions, the North Korean critic wrote, would trigger an arms race.

Pursuing more military firepower is a delicate balance for South Korea. The installation of a U.S. antimissile defense system in 2017 on South Korean soil angered China. But Beijing, while not supportive of the policy shift, is unlikely to be overly upset, said Tong Zhao, a senior fellow at the Carnegie-Tsinghua Center for Global Policy, a think tank.

“For China, South Korean missiles controlled by Seoul are less threatening than American missiles controlled by Washington," Mr. Zhao said.

After the payload restriction was lifted four years ago, South Korea developed missiles that supported warheads weighing 2 tons—all the while adhering to the maximum range of about 500 miles. That technology can easily be modified by affixing lighter warheads so that the missiles fly much longer distances, weapons experts say.

With no limits on flight distance, creating a network of military satellites would enable Seoul to become less reliant on American technology to monitor North Korea, former South Korean defense officials say.

“Having us do more of the same doesn’t hurt because it means more observability and intelligence," said Kim Byung-joo, a retired four-star South Korean army general who serves as a lawmaker in Seoul’s legislature. “It’s a case of the more, the merrier."