Japan Fires Tomahawk Missiles in East Sea for First Time; Attention Turns to North Korea's DMZ Fortification and US Shift in Tactical Nuclear Strategy

The missile can fly about 1,600 km, and if launched from the East Sea, it would put North Korea within range. This can be read as North Korea perceiving that Japan, which had until now only conducted defensive drills, has begun actual strike exercises. The move shows Japan's intent to strengthen its defense posture amid a rapidly changing Northeast Asian security environment.

Japan itself considers that it has no choice but to practice pressing this button. This is acting as a factor raising tensions with neighboring countries.

The US is accepting Japan's military buildup and judges that such moves are necessary. Analysts see Japan as being placed in an environment where it has no choice but to strengthen its military amid an increasingly complex geopolitical situation. This is coordinated with the US Indo-Pacific strategy and could bring changes to the East Asian security landscape.

Until now, Japan has conducted mainly defensive drills intercepting missiles incoming from Aegis destroyers. However, this Tomahawk launch marks the start of offensive strike training in which missiles are fired. Since the Tomahawk is not used to shoot down incoming missiles, the fact that Japan has begun practicing pressing the launch button is evaluated as an important change.

North Korea appears to be moving to turn the Demilitarized Zone (DMZ) into a de facto border. This is analyzed as having the main purposes of consolidating its regime and instilling the perception of being a completely different 'state' from the South, thereby preventing internal unrest. This DMZ fortification can be interpreted as an intent to further entrench the division of the Korean Peninsula.

North Korea's DMZ fortification also carries the possibility of a southward invasion. In a contingency, North Korea could use this fortified area for an invasion operation at any time. There are also ample factors enabling it to suddenly launch a surprise attack after assuming a defensive posture. These elements act to further raise military tensions in the DMZ area.

With the DMZ buffer zone effectively disappearing, if North Korea provokes, the South may regard it as an act of aggression and respond more forcefully. In standoff situations, accidental incidents frequently escalate into war, and the risk grows as buffer space shrinks. A wide buffer zone is what prevents accidental clashes, and if it narrows, there is always the possibility that a clash could expand greatly.

According to press reports, Patriot stockpiles have fallen from about 2,300 to around 700–800, and THAAD from 450 to around 200. This means that if something were to happen to the US mainland, interception could become difficult.

Only about 90 to 100 THAAD missiles are produced annually. This production shortfall suggests that replenishing US interceptor weapon stocks will take considerable time.

As the US weapons shortage deepens, how it sets defensive priorities will become important. Considering the time needed to refill arsenals and the changing situation, competition may arise among US allies to secure defensive priority. There is also a possibility that countries seeking to curry favor with Washington could receive help.

For example, Tokyo and Seoul could compete and argue over who will receive US defensive support first. There is a possibility of behind-the-scenes competition over who should be protected first within limited resources.

This signals a change in US defense posture to respond to a changing global security environment.

A nuclear-related change on the Peninsula is highly likely to be interpreted as part of US China strategy.

Tactical nuclear weapons are very powerful. The atomic bomb dropped on Hiroshima was also a tactical nuclear weapon, and it had destructive power capable of devastating an entire city. Therefore, an expanded role for tactical nuclear weapons could be received as a very serious and worrying matter.

China's nuclear arsenal has grown from about 200 warheads in 2020 to roughly 650 today, and is expected to exceed 1,000 by 2030, reaching a level that rivals the US. Against this backdrop, deploying tactical nuclear weapons in South Korea would be a very uncomfortable and awkward situation from China's perspective.

As a result, South Korea could once again find itself on the front line of East Asian security. This is evaluated as part of a complex security strategy.

This should be viewed not merely as a contingency against North Korea, but within the broader East Asian framework of China's possible involvement in a North Korean contingency or of pressuring China, and further within the context of US hegemonic competition. This could become a core element of US China strategy.

CSIS assessed that the Dosan Ahn Changho class could impose a real burden on the Chinese navy. This assessment appears to stem from the advantages of Korean submarines, particularly their battery-powered operation and low noise.

Submarine forces are essential for effectively controlling Chinese aircraft carrier movements. Nuclear submarines are disadvantaged in covert operations because they are noisy, whereas the Dosan Ahn Changho-class submarine can remain submerged quietly for long periods on battery power, making it assessed as the most suitable force for guarding the route of Chinese carriers and applying pressure. This stealth could impose both psychological and practical burdens on the Chinese navy.