North Korea's submarine force has been unusually active after the “hermit kingdom’s” second ICBM test-launch, according to a U.S. defense source.
American officials told CNN that two older Romeo-class submarines were deployed off Japan for about a week each – further afield and longer at sea than normal – and an additional Sang-O class sub was in the Yellow Sea on a long deployment. The activity level was "highly unusual and unprecedented," a defense official said.
CNN reports that the U.S. military has evidence that the North has recently conducted an "ejection test" of a cold-launch system for submarine-carried ballistic missiles. A cold-launch system uses steam to forcibly eject the missile from the launch tube and out of the water, preventing damage to the submarine from the ignition of the booster rocket. The test, conducted at Sinpo South Naval Shipyard, would be the fourth of its kind this year.
CSIS' Nuclear Threat Initiative believes that North Korea has been developing submarine-launched missiles and associated systems since 2013, with much of the effort centered at Sinpo. The program includes a purpose-built submarine called the Gorae (or Sinpo or Pongdae), fitted with a ballistic missile launch tube. In 2016, the North conducted several submarine-launched ballistic missile tests with a solid-fuel rocket, the KN-11 / Pukkuksong-1, including a launch into Japan's Air Defense Identification Zone (ADIZ).
The unusual submarine activity follows shortly after North Korea's second successful test of a long-range intercontinental ballistic missile. Japanese and American telemetry indicate that the ICBM achieved an altitude of 2,300 miles and a distance of 620 miles – enough for a maximum range of 6,500 miles, according to David Wright, a physicist and co-director of the Union of Concerned Scientists' Global Security Program. Wright noted that when the Earth's rotation is taken into account, this puts L.A., Denver and Chicago within range, with Boston, New York and Washington, D.C. just beyond reach. He added the caveat that the test missile's payload is unknown, and that a heavier warhead would reduce its range. North Korean state media claimed that the entirety of the U.S. mainland is within the missile’s striking distance.
On Monday, U.S. President Donald Trump told reporters that "we will handle North Korea. We are gonna be able to handle them. It will be handled. We handle everything." On Twitter, he accused China of failing to address North Korea's nuclear and ballistic missile programs. "They do nothing for us with North Korea, just talk. We will no longer allow this to continue. China could easily solve this problem!" he wrote.