Deploying North Korean Special Forces to Japan: A Potential Game Changer in the Korean Crisis

Since the signing of the Korean Armistice in 1953, North Korea’s steadfast political objective has been to reunify the two Koreas through force. In response to this persistent threat, the United States and South Korea established a mutual defense treaty in 1953 and have since developed operational plans designed primarily to repel North Korea’s initial aggression and, ultimately, advance north of the demilitarized zone (DMZ). This strategic framework has effectively prevented North Korea from launching a full-scale military aggression against South Korea over the past seven decades despite several notable skirmishes. However, two new developments are increasing the likelihood of North Korea considering a new approach: First, the miniaturization of North Korea’s nuclear warheads combined with its advanced missile capabilities, which may lead to a nuclear decoupling between the U.S., Japan, and South Korea. Second, the planned deployment of North Korean special forces to the European front starting in 2024. These factors raise the possibility that North Korea might contemplate the option of sending special forces to Japan to create chaos while simultaneously negotiating a political agreement with the South Korean government following an attempt at a full-scale military invasion of South Korea.

Although the Republic of Korea-United States Forces Korea (ROK-USFK) operational plan has been updated and modified over the years, its fundamental structure has remained largely unchanged since the original plan was developed in 1974. The plan consists of three stages: Stage One: In the event of an all-out war by North Korea against South Korea, the US-ROK combined forces would hold their positions as long as possible until major U.S. reinforcements are dispatched. Stage Two: Within two weeks, U.S. Forces Japan (USFJ) would be deployed to the Korean Peninsula to support the US-ROK combined forces and attempt to repel the North Korean forces. Stage Three: Within 90 days, the bulk of U.S. reinforcements would be sent from the continental U.S., ultimately turning the tide of the war and driving back North Korean aggressors. This structure means that if any issues arise in fully implementing Stages 2 and 3, North Korea could potentially occupy part of South Korea, establish a new defensive perimeter, and effectively create a fait accompli, indefinitely altering the balance of the conflict.

Fully aware of the risks (such as the potential disruption of Stages 2 and 3), the United States has consistently reaffirmed its commitment to supporting South Korea in the event of a Korean contingency. Meanwhile, the U.S. and Japan have been developing a joint operations plan, most notably OPLAN 5055, to address such a scenario. However, growing concerns about nuclear decoupling between the United States, Japan, and South Korea—due to North Korea’s advancing nuclear capabilities, including the ability to target U.S. territory—have increased the possibility that North Korea might initiate military operations against South Korea, thereby pressuring both the U.S. and Japan to stay out of the conflict. As North Korea’s nuclear capabilities continue to improve, such as acquiring reliable Multiple Independently-targetable Reentry Vehicles (MIRVs) and missiles capable of performing irregular maneuvers to evade interception, the likelihood grows that North Korea could leverage nuclear blackmail to create division among the U.S., Japan, and South Korea, settling scores with South Korea using only conventional forces. North Korea seeks to sow doubt among the United States’ key allies in the region—Japan and South Korea—about the credibility of the U.S. commitment to retaliate with nuclear weapons, which may lead to potential nuclear decoupling and North Korea launching a full-scale war against South Korea. Simultaneously, North Korea might deploy special forces to Japan to carry out sabotage operations aimed at disrupting the smooth implementation of Stage Two, specifically the dispatch of U.S. Forces Japan (USFJ) to the Korean Peninsula. This scenario has been discussed by U.S. and Japanese officials since the post-Cold War period. For example, the Concept Plan 5055, a U.S.-Japan combined concept plan formulated in 2002 to address a North Korean contingency, envisioned hundreds of North Korean guerrillas infiltrating metropolitan areas, targeting critical facilities such as nuclear reactors and USFJ installations, including airfields. In response to such incursions, the plan designated 135 critical facilities for defense, assigning responsibility to Japan’s Ground Self-Defense Forces (SDF). If North Korean commandos were to wreak havoc within Japan, it could demoralize Japan and cause hesitation in providing logistical support to USFJ. At this critical juncture, North Korea might secure portions of South Korean territory and pursue political agreements with the United States, potentially leaving South Korea more vulnerable to nuclear blackmail. These developments would significantly undermine trilateral security cooperation among the U.S., Japan, and South Korea.

North Korea’s potential infiltration of special forces into Japan should be taken seriously. While the Maritime Self-Defense Force (SDF) and the Japanese Coast Guard would maintain heightened vigilance against North Korean espionage vessels in the event of a Korean contingency, even a relatively small number, such as 50 North Korean special forces operatives, could cause significant damage on Japanese soil. It is important to note that in 1968, 33 North Korean special forces nearly assassinated the South Korean president, and in the 1996 Gangneung submarine infiltration incident, it took 60,000 South Korean troops 50 days to eliminate just 20 North Korean agents. Unlike the North Koreans sent to Europe to fight against Ukrainian forces—who were poorly supplied, lacked foreign language skills for communication with Russian forces, and had to fight in a terrain vastly different from North Korea—North Korean special forces deployed to Japan would be relatively small in number but highly trained, elite commandos. Crucially, they would bring with them valuable combat experience gained from the recent conflict between Ukraine and Russia.

To address the aforementioned threats, the Japanese Self-Defense Forces (SDF) have been preparing for irregular warfare scenarios in cooperation with the United States over the years. However, it would be highly advisable for Japan to also collaborate with South Korean counterparts to further strengthen their readiness against North Korean infiltration. With this in mind offer the following policy recommendations. First: intelligence sharing between South Korea and Japan. By doing so, Japan could gain valuable insights into potential infiltration routes, sabotage tactics, and previous instances where North Korea has deployed special forces against external targets. Second: joint training and exercises between South Korea and Japan. South Korean military units, particularly special operations forces, could engage in joint training with the Japanese SDF, enhancing their combined capabilities in countering irregular warfare. Third: strategic advice on nuclear security. South Korea’s experience in managing the security of nuclear facilities could be extremely beneficial for Japan in refining and strengthening its own nuclear security protocols. While North Korea’s growing nuclear capabilities remain a primary concern for the United States, Japan, and South Korea, it is equally crucial for the three countries to prepare for the possibility that North Korea might launch a simultaneous irregular and conventional military operation with the more limited objective of occupying a portion of South Korea. Such an action would have a devastating psychological impact on the U.S., Japan, and South Korea. To prevent this dangerous scenario, Japan and the U.S. must urgently explore ways to bolster the security of potential targets within Japan. In this context, South Korea should offer valuable intelligence on North Korean special forces, including insights obtained from the recent Ukraine-Russia war (should any captured North Korean soldiers be sent to South Korea). Additionally, if needed, South Korea should participate in joint training and military exercises to bolster preparedness.