July 8, 2026

It has come to light that in a U.S.-led multilateral live-fire sinking exercise (SINKEX), a Maritime Self-Defense Force submarine fired a torpedo and sank a target warship.

The SDF’s participation in such a military drill totally departs from Japan’s “exclusively defensive defense” policy.

Furthermore, this indicates that in line with U.S. Secretary of Defense Hegseth’s remark, steps are being taken to place Japan at the forefront of tensions between the United States and China. Hegseth in March 2025 at a press conference after the Japan-U.S. Defense Ministerial meeting in Tokyo remarked that mainly with a possible “Taiwan contingency” in mind, Japan would be on the frontlines of any contingency in the western Pacific.

The MSDF joined in the U.S.-hosted multinational joint field training exercise Valiant Shield 2026 which took place between June 22 and July 1 across a wide expanse of the Pacific. The drill in question was held during Valiant Shield in the Philippine Sea on June 26. It is believed that this SINKEX was conducted with the aim of containing China’s expanding presence in the Pacific.

The U.S. military on that day released images of a target ship (the decommissioned amphibious transport dock USS Juneau) exploding after being hit by a torpedo fired from the MSDF submarine “Jingei”.