MELBOURNE, Australia — A Japanese submarine is damaged after colliding with a commercial ship in international waters off Japan on Monday, resulting in slight injuries to three crew members.

According to Japan’s Ministry of Defense, the diesel-electric submarine JS Soryu hit the commercial bulk carrier Ocean Artemis as it was surfacing in waters south of Cape Ashizuri in Kochi prefecture on the Japanese island of Shikoku on Monday morning local time.

The ministry added that the damage sustained by the Soryu was worse than initially thought, with the conning tower warped and the starboard hydroplane — which is used to adjust the submarine’s depth underwater — almost broken off.

The collision also damaged the antenna mast array of the submarine, which includes the periscope and communications antenna, leaving the Soryu unable to report the incident via normal communications channels.

As a result, the submarine, which was on a training sortie when the incident occurred, had to get within mobile phone coverage before being able to contact the Kure naval base to report the incident.

However, the submarine was able to sail under its own power to the nearby port of Kochi, and the three injured crew members were not seriously injured and did not require evacuation to a hospital.

The Soryu’s home port is normally the Japan Maritime Self-Defense Force’s base at Kure. The boat is part of Submarine Squadron Five of the JMSDF’s 1st Submarine Flotilla. The 2,950-ton, 84-meter submarine is the lead boat of a class of 12, and it is widely regarded as one of the best diesel-electric submarine designs in the world.

Taking a closer look

Japan’s Coast Guard said it is investigating the incident and the JMSDF is assessing the damage to the submarine.

Collin Koh, a research fellow at the Institute of Defence and Strategic Studies at the S. Rajaratnam School of International Studies in Singapore, told Defense News that based on photos released by the Japanese Coast Guard, it does not appear that the submarine’s pressure hull was damaged.

He added that while the damage looks like it could be repaired with relative ease, “the boat will still have to undergo post-repairs trials to evaluate its quieting ability — that is, to ensure the boat passes the required standards for acoustic signature while underway in order to be deemed operationally ready and safe to reinstate into service.”

That process could take months, if not a year to complete.

However, Koh does not foresee a submarine gap for the JMSDF due to the Soryu being out of action during repairs. He noted that Japan has a fleet of 22 submarines as well as two training submarines in service.

What might affect the tempo of JMSDF submarine operations in the wake of the collision is the likelihood that there will be a comprehensive review and reassessment of operational safety norms in the wake of this high-profile incident. That could place further strain on a force that has admitted to being under pressure from an expanding set of mission demands.

Mike Yeo is the Asia correspondent for Defense News.

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