North Korea’s firing of a sea-based ballistic missile during the weekend represents another step forward in the rogue regime’s relentless efforts to make its nuclear threats more tangible.

The submarine-launched ballistic missile flew only some 30 kilometers, far short of the 300 km range needed to qualify as an SLBM. But the test launch cannot be seen as a complete failure, given the progress made in undersea ejection capability.

In 2015, the North conducted two ejection tests for a sea-based ballistic missile, first in May and second in November. Compared with these two previous tests, the latest one was more successful in terms of ejection capability.

Military experts in Seoul believe that the North fired a solid-fuel rocket on Saturday, abandoning the liquid-fuel system that has failed in the past.

They say North Korea appears to have decided to switch to a solid-propellant design as it is more stable and robust than a liquid-fuel system.

Having made some headway in SLBM technology, North Korea is expected to undertake more test launches in the future as it is keen to enhance its nuclear delivery capability.

The South Korean Defense Ministry expects that the North is likely to deploy SLBMs within the next three to four years for actual combat use.

Military experts say that the North may have already started to develop a 3,000-ton submarine that can provide a stable platform to launch multiple SLBMs.

For the Saturday test fire, the North used a 2,000-ton Sinpo-class submarine, which can launch only one SLBM from about 10 to 15 meters underwater, a depth that exposes the submarine to the risk of detection. To avoid detection, a submarine should be capable of going down some 50 meters underwater.

If North Korea builds bigger submarines carrying multiple ballistic missiles, they would make its nuclear threats more potent, as the mobile sea-based ballistic missiles are much harder to detect.

As North Korea’s SLBM threat increases, the South Korean government needs to step up its counter-submarine capabilities.

For an early detection of the movements of the North’s submarines, the government needs to launch more advanced satellites and introduce early-warning anti-ballistic missile radar. It also needs to deploy more sea-borne patrol aircraft.

It will also have to build and deploy more Aegis warships to detect and destroy the North’s incoming missiles. Bigger submarines with powerful offensive capabilities are also needed to attack the North’s submarines.