North Korea Fires Two Short-Range Ballistic Missiles on September 20, 2026, Testing Maritime Vigilance of Japan, the U.S., and South Korea

On September 20, North Korea launched two short-range ballistic missiles toward the East Sea (Sea of Japan). This was reported successively by the South Korean Joint Chiefs of Staff, Japan Times, Kyodo News, and UPI. There is no information indicating that the missiles fell within Japanese territory or its exclusive economic zone, and no direct damage has been confirmed at this time.

Timing After Exercises

This launch comes immediately after the trilateral exercise Freedom Edge 26 conducted by the United States, Japan, and South Korea from September 7 to 11. North Korea also launched a ballistic missile on September 12, and these two missiles should be viewed not merely as a single act of intimidation but as a continuous signal to gauge the post-exercise alert status and political reactions. There remains a discrepancy between the training details released by the Korean People's Army and the flight information obtained by South Korea, so it is necessary to refrain from definitive conclusions regarding the type and flight parameters.

Burden on the Japan-U.S.-South Korea Air Defense Network

Even if they are short-range, if the launch sites are dispersed, if there is simultaneous approach from multiple directions, and if the launch intervals are shortened, the burden on the intercepting side will increase. The Japan Maritime Self-Defense Force's escort ships, the Japan Air Self-Defense Force's air surveillance and control units, and the intelligence and surveillance assets of the U.S. and South Korea must simultaneously process not only the missiles themselves but also the detection of launch signs and the sharing of flight path information. The value of Japan-U.S.-South Korea cooperation lies not in aligning post-launch announcements but in shortening the time from detection to alert and the alteration of naval vessel routes.

Blind Spots in SLOC Protection

For Japan, it is not only important whether the projectiles reach Japan. Commercial vessels, aircraft, and Japan Maritime Self-Defense Force ships passing through the Sea of Japan are forced to reconfirm navigation information each time a launch occurs. This is both a matter of interception capability and an issue that raises the operational costs of SLOC (Sea Lines of Communication). When discussing missile defense, the Ministry of Defense tends to focus on the interception capabilities of Aegis ships, but in practice, setting up alert maritime areas and rapidly communicating information to civilian vessels carry equal weight.

In my view, what these two missiles indicate is not that North Korea has unveiled new weapons, but rather that it recognizes its ability to constrain the decision-making of Japan, the U.S., and South Korea even after the exercises.

Limits of Political Signals

Even in situations where contact with the United States and the possibility of summit diplomacy are being discussed, Pyongyang has not relinquished military pressure. Therefore, interpreting the launches as immediate evidence of a refusal to negotiate or dismissing them as mere routine training is premature. When separating capability from intent, the core of this situation lies in the repetition of short-range attacks in terms of capability and the verification of response speed to Japan-U.S.-South Korea cooperation in terms of intent.

The true blind spot is not just whether missiles can be intercepted. It lies in how much the operations of commercial vessels, aircraft, and naval vessels can be disrupted with each launch, and how quickly the three countries can form a shared situational awareness.

Main Sources

• Japan Times: North Korea fires off two ballistic missiles (September 20, 2026)
• Kyodo News: North Korea fires short-range ballistic missiles toward Sea of Japan (September 20, 2026)
• UPI: North Korea fires short-range ballistic missile toward East Sea (September 20, 2026)
• Japan Maritime Self-Defense Force: Public materials on U.S. and multilateral exercises in September 2026