North Korea’s missile activities have grown unprecedentedly intense in the past year. Pyongyang has been pursuing a large-scale modernization agenda first outlined in 2021 while also stepping up its rehearsals for possible nuclear war in new ways. These developments have unnerved both South Korea and Japan and increased the burdens on both states as they seek to track, assess, and analyze the contours of North Korea’s missile activities. Seoul is also growing increasingly uneasy about the implications of Pyongyang’s advances for the credibility of U.S. extended deterrence reassurances, manifesting in an broad national debate on whether it should seek answers to the challenges it faces with nuclear weapons of its own.
Amid these changing dynamics, the United States should expand the scope of intelligence about North Korean missile launches that it shares in near real time with its Northeast Asian allies. This would not be a panacea for the growing array of missiles that North Korea might be able to deploy in a conflict, but it would meaningfully increase the security of both South Korea and Japan while strengthening trilateral cooperation. Specifically, Washington should develop a secure intelligence-sharing protocol that would provide Seoul and Tokyo with prompt access to relevant assessments acquired from the United States’ Space-Based Infrared System (SBIRS). Doing so would bolster allied reassurance and potentially mitigate incentives for North Korea to probe the limitations of missile warning capabilities in South Korea and Japan.
Space-based infrared missile detection is the backbone of the U.S. early warning system. SBIRS satellites are calibrated to spot the intense infrared signatures generated by the fiery plumes of boosting missile stages of all ranges, allowing for the prompt detection of launches tens of seconds after engine ignition.
SBIRS is instrumental for the United States in understanding and assessing the use of missiles in testing, exercises, and war worldwide. SBIRS-derived data has been critical to the United States’ own situational awareness efforts in Europe in the past year. For instance, public quantitative assessments about the numbers of missiles used by Russia—and their rates of success—in its war on Ukraine are almost surely largely derived from SBIRS-sourced data. Likewise, U.S. intelligence efforts to understand Pyongyang’s progress have benefited substantially from data derived from these sensors.
Due to cost and complexity, capabilities analogous to SBIRS are not available to South Korea and Japan, which rely entirely on land- and sea-based radars, supplemented by other limited forms of collection, to track and detect missiles launched at or near their territories. While both countries have plans to deploy new military reconnaissance satellites, neither plans to employ a persistent space-based missile warning capability. Seoul and Tokyo are further mulling bilateral radar information sharing amid a broader improvement in bilateral ties since the arrival of conservative South Korean President Yoon Suk-yeol. They both benefit from voluntary trilateral information sharing by the United States pursuant to the 2014 Trilateral Information Sharing Arrangement, in addition to their respective bilateral alliance information exchanges.
Unfortunately, these means are not adequate. On several occasions, Seoul and Tokyo have struggled to assess—at least in real time—the nature of North Korean missile launches. Last month, for example, North Korea launched two “tactical nuclear” missiles into the East Sea. In the moments after the launch, South Korea’s Joint Chiefs of Staff issued a statement noting that two missiles had been detected, while Japanese authorities initially reported that at least three missiles had been launched. Tokyo later updated its assessment to two missiles, which matched North Korea’s own claim about the launches, published a day later in its state media. Two months before that, Tokyo detected and warned that North Korea had launched a single missile as part of a drill, while Seoul detected the launch of two missiles. Even when the two agree on missile numbers, they might disagree on the range or maximum altitude.
North Korea’s development of an increasingly diverse range of missile types since 2019 has introduced new complexities for missile tracking. For instance, Pyongyang has started regularly launching endoatmospheric gliding missiles, which fly low in the atmosphere compared to other ballistic missiles and can occasionally underfly radar detection entirely. In both 2019 and 2021, some missile launches went unreported by South Korean authorities, with initial notification coming from U.S. officials who spoke anonymously to reporters. More recently, both South Korea and Japan have struggled to detect the launch of ballistic missiles with very short ranges. In April 2022, North Korea tested two new close-range ballistic missiles that flew at low altitudes and ranged only 110 kilometers or so. This test went entirely unreported in real time by South Korean and Japanese authorities. Instead, it was picked up by the United States, presumably using SBIRS, and first reported publicly by U.S. authorities in Guam. New cruise missiles, too, have presented difficulties for both Seoul and Tokyo.
These incidents have not gone unnoticed by North Korea. Pyongyang tracks missile defense developments closely, with even leader Kim Jong Un taking note of prominent U.S. and allied missile defense tests. After South Korean authorities released incomplete information concerning a missile launch in 2019, a statement attributed to Kwong Jong Gun, director-general of the Department of American Affairs at the North Korean Foreign Ministry, dubbed Seoul a “global laughing stock . . . because it had failed to calculate properly the range of the power demonstration firing of our army.”
North Korea’s belief that South Korean and Japanese warning capabilities are inadequate may have more serious consequences than gloating. It could undermine deterrence and even incentivize launches. Missile warning and tracking capabilities are required to effectively cue missile defense systems, which comprise an important part of both Seoul’s and Tokyo’s approaches to limiting damage from potential North Korean attacks. Repeated lapses in missile tracking—whether real or perceived—could engender confidence (and perhaps overconfidence) in Pyongyang about the military effectiveness of its missiles, undermining deterrence in wartime. Meanwhile, in peacetime, Pyongyang may be prompted to carry out missile launches to evaluate and probe the limits of regional missile warning capabilities. Assessments about those launches from Seoul and Tokyo—especially incorrect assessments—have intelligence value to Pyongyang.
One solution to these problems would be for both Seoul and Tokyo to simply cease prompt public reporting on North Korean missile events. This is, however, unlikely to be feasible. As liberal democracies with governments accountable to their citizens, both have good reasons to keep the public informed in real time.
A better option would be for the United States to share high-fidelity SBIRS data with Seoul and Tokyo to improve their ability to rapidly and accurately characterize the numbers and types of missiles launched by North Korea. Meanwhile, each can continue to refine and improve their own missile warning and tracking capabilities.
Washington, Seoul, and Tokyo all seem to support moves in this direction. In November, Yoon, U.S. President Joe Biden, and Japanese Prime Minister Kishida Fumio jointly stated that they “intend to share” North Korean missile warning data in real time Their declaration described such a measure as “a major step for deterrence, peace and stability.” However, since this statement, the three countries have provided little clarity on how they might proceed beyond general assurances that consultations on North Korea take place regularly. In its National Defense Strategy, the Biden administration further identified trilateral U.S.-Japan-South Korea information sharing as an important priority.
An important and practical consideration for Washington will be information security, which has traditionally been a hindrance in advancing alliance cooperation in Northeast Asia. Because the existence of SBIRS is no secret, even if data derived from the constellation is tightly held, sources and methods concerns should not preclude sharing with allies. However, North Korean offensive cyber campaigns have been successful in penetrating militarily sensitive sites and systems in South Korea, and Japan is concerned about similar vulnerabilities, so the United States may be worried that Pyongyang could acquire any data provided to Seoul and Tokyo.
For this reason, the United States may not wish to grant them access to the raw SBIRS data that is processed and securely analyzed by U.S. personnel. Instead—and with the spirit of reaching near-real-time fidelity, as noted in the November declaration—the United States should study the viability of setting up a rapid data dissemination mechanism that would share processed, early assessments of missile events originating in North Korean territory from SBIRS with relevant entities in South Korea and Japan. (To the extent feasible, these assessments could be supplemented by inputs from regional radars and other capabilities, including surveillance aircraft.) The scope of information that is ultimately shared could include little more than the numbers of missiles detected and their likely type.
In practice, achieving near-real-time fidelity would mean turning around assessments in a minute or two after detection. This goal should be feasible: U.S. assessments of missile threats to its own homeland take place on similar timescales. In early 2022, a mistaken North American Aerospace Defense Command assessment of a North Korean missile launch resulted in the issuance of a ground stop for U.S. civilian air traffic. The ground stop was issued at precisely the minute the missile launch was initially detected. Despite this existing capability, setting up an arrangement for allies would likely require the U.S. Space Force to devote dedicated personnel to the allied data-sharing mechanism.
By avoiding direct access to the raw SBIRS data, Washington can also assuage concerns that it is seeking to network missile defense assets based in South Korea and Japan into its own homeland missile defense efforts—a criticism that will likely emerge from Beijing, should such cooperation proceed. China has long alleged that the United States is seeking to incorporate radars and potentially interceptors on allied soil into its homeland missile defense efforts. While Beijing will likely be critical of any measures to promote greater trilateral missile-related information sharing, the United States should nevertheless take steps to offer assurances that this North Korea–specific measure would not threaten China’s strategic deterrent or even conventional military forces.
Politically and diplomatically, this type of intelligence sharing could lead to the development of important new habits of cooperation between Seoul and Tokyo and even facilitate greater bilateral cooperation between them, suiting U.S. regional goals. Meanwhile, this proposal would contribute to reassuring both Seoul and Tokyo amid growing concerns that Washington is either overly distracted by its focus on China and Russia or insufficiently concerned by North Korea.
For instance, despite North Korea’s unprecedentedly intense year of missile launches in 2022, the United States provided relatively little information about them—all while offering regular public updates on Russia’s use of missiles and other capabilities against Ukraine, a non-treaty ally. The sole notable act of U.S. declassification and public dissemination concerning North Korean missile capabilities took place in March 2022, when the Department of Defense declared that an alleged North Korean satellite test involved components associated with a new intercontinental-range ballistic missile (ICBM).
While this disclosure was commendable, it also may have contributed to views in Seoul and Tokyo that the United States is primarily and perhaps disproportionately concerned with North Korea’s development of ICBMs capable of threatening the United States and comparatively less so with shorter-range missiles that exclusively hold South Korean and Japanese territory at risk. This impression would be regrettable and even detrimental to alliance unity at a time when concerns about so-called decoupling are growing. Proactive U.S. information sharing, irrespective of missile type, can remediate this and reassure Seoul and Tokyo that Washington shares their threat perceptions.
As the North Korean missile threat reaches unprecedented heights, the task of reassuring allies in Northeast Asia should take on new urgency for the United States. Yoon’s remarkable public contemplation of South Korea possibly pursuing nuclear weapons speaks to the need for creative new means of advancing shared security for the United States and its Northeast Asian allies. Consultations, renewed military drills, and tabletop exercises will continue to be a meaningful component of reassurance, but Washington should also be prepared for bold overtures to its allies that demonstrate shared stakes in peace and security in Northeast Asia. One way to do that is to open the aperture on missile-related information sharing.
The author is grateful to Lisa Michelini for research assistance with this piece.