North Korea's Naval Buildup Will Stretch Allied Forces Across the Indo-Pacific

North Korea’s naval modernisation is still in its early stages. Much of its surface and submarine fleet remains outdated, while its more ambitious shipbuilding and undersea programs face serious technical and operational obstacles.

North Korea is gradually constructing a layered maritime force rather than a conventional fleet. Missile-armed destroyers, ballistic-missile submarines, coastal anti-ship missiles, mines and unmanned systems could operate as interconnected parts of a wider coercive strategy.

North Korea’s 5,000-tonne Choe Hyon-class destroyers, first unveiled in 2024, are the most visible expression of its expanding naval ambitions. The first Choe Hyon-class destroyer was successfully launched in April 2025. Their combat effectiveness remains uncertain. The accident during the launch of the second vessel exposed weaknesses in its shipbuilding capacity.

The greater concern is the interaction between these ships and North Korea’s improving undersea capabilities. Pyongyang operates a large, mostly obsolete submarine fleet. But it has also launched the diesel-powered Hero Kim Kun Ok, described as a tactical nuclear-attack submarine. North Korea has continued work on submarine-launched ballistic and cruise missiles, and displayed what it says is a nuclear-powered submarine under construction.

None of these projects should yet be assumed to provide a reliable operational capability. Together, however, they reveal a consistent effort to move part of North Korea’s nuclear force to sea.

A stronger submarine force would increase the survivability and unpredictability of North Korea’s nuclear posture. Land-based missiles can be monitored through known operating areas, support vehicles and launch preparations. Submarines are harder to locate and can threaten targets from less predictable directions. Their deployment could force the allies to begin intensive searches before there was clear evidence that Pyongyang intended to launch.

Missile-armed surface ships would further increase the versatility of North Korea’s nuclear forces. Nuclear weapons could be distributed across fixed and mobile land launchers, submarines and surface vessels. This would not necessarily make the arsenal more accurate or reliable, but it would make its employment more flexible.

Pyongyang could use maritime nuclear forces for retaliatory strikes, limited demonstrations, attacks on ports and naval bases, coercive deployments or attempts to separate South Korea and Japan from the US. The distinction between conventional and nuclear operations would become less clear if the same ships or submarines could carry both types of weapons.

This ambiguity would impose real costs. The allies would need to monitor North Korean ports, shipyards, submarine bases and coastal operating areas continuously. Additional maritime surveillance and anti-submarine warfare assets might be required to track potentially nuclear-armed vessels.

Mines, coastal missiles, decoys and unmanned systems could deepen the burden. Individually, many North Korean ships and aircraft may be vulnerable. Used together, they could complicate access to ports, threaten reinforcement routes and delay allied naval operations near the peninsula.

The regional implications would become most serious during simultaneous crises. If tensions rose on the Korean Peninsula while a confrontation developed across the Taiwan Strait, increased North Korean submarine and surface activity could restrict the ability of the US and Japan to move naval and surveillance assets elsewhere.

Washington would have to decide whether to retain scarce anti-submarine and missile-defence forces around the Koreas or redirect them towards a wider regional contingency. Moving them southward could weaken deterrence on the peninsula, but keeping them in Northeast Asia would reduce the forces available elsewhere.

North Korea’s objective may therefore be less about controlling the sea than controlling allied attention. Its navy does not need to defeat the allies. It needs to create sufficient uncertainty that they cannot safely ignore it.

The allies should not exaggerate North Korea’s capabilities. Its naval transformation will be slow, uneven and vulnerable to technical failure. But waiting until its new submarines and surface ships become fully operational would be unwise. Their significance lies in how they could broaden the survivability, flexibility and potential employment of North Korea’s nuclear arsenal.

North Korea’s naval buildup remains immature. It is nevertheless changing from a coastal force into a diverse instrument of nuclear coercion – one capable of tying down allied forces in Northeast Asia and complicating maritime strategy across the western Pacific.

Jihoon Yu is a research fellow at the Korea Institute for Defense Analyses and was the main author of a 2010 policy document for the South Korean navy’s development up to 2045.

AI contributed no ideas to this article – Jihoon Yu.

This article appeared originally at The Strategist (ASPI).