North Korea on Wednesday accomplished what is assessed to be the first successful firing of a submarine-launched ballistic missile into the East Sea, in what appears to be an act of protest against ongoing annual joint drills held by South Korea and the US.

The launch comes two days after the North threatened a “pre-emptive nuclear strike” against the allies, claiming it to be retaliatory action against the military exercise.

According to the Joint Chiefs of Staff, the SLBM was fired at around 5:30 a.m. near the city of Sinpo, South Hamkyung Province. It added that the missile appears to have fallen in Japan’s air defense identification zone.

“The SLBM appears to have flown about 500 kilometers, which would indicate progress compared to past few test flights,” the JCS said, adding the allies are conducting a detailed analysis of the launch. It said that the launch marked a severe violation of the UN Security Council resolution and presents a grave threat to the regional security.

The UNSC resolution bans Pyongyang from developing any ballistic missiles or nuclear programs. In March, the UNSC adopted a new resolution that encompasses the strongest economic sanctions to date against the North.

While the actual flight of the missile is much shorter than its perceived maximum range of 2,500 kilometers, the military is evaluating the launch to have been a success. This is because the missile is believed to have been deliberately launched at a higher degree and with less fuel than normal to invade as little as possible of Japanese air space.

When fired via the conventional method, fully charged with fuel, it is believed to be able to fly over 2,000 kilometers.

The latest launch marked the fourth time this year the communist state has fired an SLBM. It has test-fired more than 30 ballistic missiles since current leader Kim Jong-un started to helm the country in 2011.

Wednesday’s launch also dealt a blow to the military’s initial estimate that the North’s SLBM capacity is in its earliest stages, lacking actual ability to fly the missile for a significant range. The military reportedly believes that Pyongyang’s SLBM is in the flight-testing stage, while short of being tested for its actual functions as a ballistic missile.

The North’s success also considerably moved up the expected timeline of the SLBM’s actual deployment -- originally put at around 3-4 years -- with some estimating that it could be deployed as early as later this year.

Although the North has only one 2,000-ton class submarine where it can launch the SLBM from, it is believed to be able to develop the missiles itself on its own, regardless of the UN sanctions that it has been put under since March.

The missile is assessed to have used solid-fuel engine, due to stability issues, and its maximum speed is estimated to be around Mach 10.

Local observers believe that the missile launch is a form of protest against the Seoul-Washington Ulchi Freedom Guardian drills scheduled from Aug.22-Sept.2. North Korea has labelled all drills by the allies as preparations for an invasion of its territory.

But the Neutral Nations Supervisory Commission has backed the allies’ claim that the drills are non-provocative in nature and is strictly for defensive purposes. Switzerland and Sweden monitor the annual exercises, including the UFG, to ensure that they are in compliance with the 1953 armistice agreement that ceased the 1950-53 Korean War.

“I believe the meaning of the SLBM launch is threefold: One is to as a countermeasure against the UFG; the second is a protest against the possible strengthening of the military alliance among Seoul, Washington and Japan. Lastly, it is to show that North Korea has succeeded in diversifying the means of delivering a nuclear warhead,” said Kim Yong-hyun, a professor of North Korean studies at Dongguk University.

This June marked the first time the North successfully launched its intermediate-range Musudan missile. The Musudan is believed to have maximum range of 3,000 kilometers, putting the US military base in Guam within its striking range.

Kim speculated that Pyongyang may conduct another SLBM launch soon to prove its capacity.

The successful test launch of an SLBM also raised more questions over the effectiveness of the US Terminal High Altitude Area Defense system, scheduled to be deployed in the South by next year.

From the perspective of speed, the THAAD can intercept missiles that are moving as fast as the SLBM did during Wednesday’s launch. But the fact that an SLBM is fired from a submarine would theoretically enable it to be launched from a location which THAAD cannot detect.

The military has said that it is working on supplementing the countermeasures for missiles fired outside the THAAD radar’s range. This implies that as of now, it is yet unable to detect or counter ballistic missiles fired behind THAAD’s back.

By Yoon Min-sik (minsikyoon@heraldcorp.com)