North Korea's Launch of 12 Super Large 600mm Multiple Rocket Launchers and a New Phase in Northeast Asian Security: Responses and Challenges for the Japan-U.S. Alliance

On March 14, 2026, North Korea publicly conducted a training exercise by launching 12 rounds of its 600mm caliber super-large multiple rocket launcher (KN-25) simultaneously, hitting island targets in the Sea of Japan. This test firing, which was directly observed by Kim Jong-un, General Secretary of the Workers' Party of Korea, was not merely a technical demonstration but sent a complex message regarding the security structure in Northeast Asia.

The KN-25 is considered a tactical weapon with a range of 420 to 364 kilometers, developed with the assumption of carrying tactical nuclear warheads. After the inspection, Kim Jong-un stated, "The training will deeply make the enemy within the 420-kilometer range understand the destructive power of tactical nuclear weapons," clearly aimed at South Korea and the U.S. forces stationed in South Korea. Given its range, this weapon system can reach central South Korea, including Seoul, and U.S. military bases in South Korea are also within its range. According to analyses by U.S.-South Korea military and the Institute for the Study of War (ISW), North Korea launched a total of more than 10 ballistic missiles toward the Sea of Japan around the same date, marking the third ballistic missile launch this year.

This provocative act coincided with a temporary decline in the air defense capabilities of the U.S. Forces Korea (USFK). According to an ISW report dated March 18, USFK redeployed Patriot PAC-3 missile interceptors and the THAAD (Terminal High Altitude Area Defense) system to the Middle East in early March. Reports from South Korean media confirmed that on March 3, THAAD launchers were transported from the Seongju base, and as of March 13, only one of the six had returned. Since 2017, South Korea has relied on this THAAD battalion to maintain interception capabilities at altitudes of 40 to 150 kilometers, making this gap significant. South Korean President Lee Jae-myung opposed this redeployment, but was unable to overturn the U.S. decision.

In response to this air defense gap, Japan, the U.S., and South Korea held missile provocation response consultations on March 16. The Japanese government utilized its own intelligence-gathering capabilities for detecting and tracking missile launches, and according to the Ministry of Defense, the launched ballistic missiles were analyzed to have fallen into the Sea of Japan outside Japan's Exclusive Economic Zone (EEZ). However, there is a growing recognition within defense authorities that the current Japanese interception system has limitations in responding to the enhancement of North Korea's missile capabilities.

In response to these security threats, Japan is making fundamental efforts to significantly increase its defense budget and acquire stand-off strike capabilities. The defense buildup plan has advanced the goal of raising defense spending to 2% of GDP from fiscal year 2027 to April 2026, achieving this target. The supplementary budget approved by the Cabinet in December 2025 allocated an additional approximately 1.1 trillion yen (about 7 billion dollars) for defense spending, bringing the annual defense budget to about 10 trillion yen.

Moreover, it is significant that Japan is making concrete procurements toward acquiring "counterstrike capabilities (enemy base attack capabilities)." Japan is procuring 400 Tomahawk cruise missiles with a range of approximately 1,600 kilometers for about 2.35 billion dollars (approximately 350 billion yen) through the Foreign Military Sales (FMS) program with the U.S. Additionally, the improved Type 12 surface-to-ship guided missile being developed by Mitsubishi Heavy Industries is also being enhanced for longer ranges, expected to exceed 1,000 kilometers in the future. These capabilities are attracting attention both domestically and internationally as they represent a significant shift in the interpretation of Japan's traditional defense posture.

On the other hand, the diplomatic environment surrounding North Korea is also changing. In relations with China, passenger train services between Beijing and Pyongyang resumed on March 12, and Air China announced the revival of regular flights for the first time in six years on March 30. While North Korea is strengthening its ties with Russia, it is also seeking to secure tourism revenue through the normalization of economic relations with China. China, for its part, is seeking leverage to regain some influence over North Korea, which is increasingly leaning toward Russia, creating a complex intertwining of interests between the two countries. Whether North Korea will resume accepting Chinese tourists, who could generate over 175 million dollars in annual tourism revenue, will be a key indicator for understanding future diplomatic trends.

The security environment in Northeast Asia is undergoing complex and rapid changes. North Korea continues to qualitatively improve its nuclear and missile capabilities, conducting training with the practical use of tactical nuclear weapons in mind. The U.S. has redeployed air defense assets from the Korean Peninsula to the Middle East to respond to global security demands, leaving South Korea with a defense gap. Japan is enhancing its deterrent capabilities through historical defense buildup and the acquisition of counterstrike capabilities, but this process is intensifying strategic competition with neighboring countries, particularly China.

There are three focal points for the future. First, how to fill the gap until the USFK's air defense systems (THAAD and Patriot) fully return from the Middle East. Second, whether Japan's acquisition of counterstrike capabilities and deployment of Tomahawks will function as an actual deterrent. Third, how North Korea's rapprochement with China will influence the external actions of the Kim Jong-un regime. Strengthening cooperation among Japan, the U.S., and South Korea is essential, but maintaining the alliance's reliability and responsiveness will remain the biggest challenge as the prioritization of U.S. global security resource allocation fluctuates.