Summary (tl;dr)

U.S. and allied forces participating in Exercise Valiant Shield 2026 recently conducted a live-fire sinking exercise (SINKEX) in the Pacific Ocean, successfully sinking the decommissioned USS Juneau (LPD-10) with a torpedo strike from a Japanese submarine as part of a multi-domain assault.

Essential Background

Valiant Shield is a major biennial multinational military exercise led by the U.S. in the Indo-Pacific region, involving allied nations such as Japan, Australia, Canada, and New Zealand. Its primary purpose is to enhance interoperability among participating forces across air, sea, land, space, and cyberspace, focusing on detecting, tracking, and engaging targets. Sinking exercises (SINKEXs) are crucial components of these large-scale drills, providing realistic training opportunities for forces to employ weapons and refine targeting skills against an actual vessel in conditions that cannot be fully replicated by simulators. The USS Juneau (LPD-10) was an Austin-class amphibious transport dock, commissioned in 1969, which saw service in conflicts like the Vietnam War and Operation Desert Storm before its decommissioning in 2008.

The Full Story

During Exercise Valiant Shield 2026, which ran from June 22 to July 1, 2026, U.S. Pacific Command joint forces, alongside allied and partner forces, executed a live-fire sinking exercise (SINKEX) on June 27, 2026. The target for this advanced training scenario was the decommissioned USS Juneau (LPD-10). The culminating blow to sink the vessel came from a torpedo strike fired by a Japan Maritime Self-Defense Force submarine. Prior to the torpedo strike, other assets, including a U.S. Navy P-8A Poseidon aircraft with a Harpoon missile and a U.S. Air Force B-2 Spirit bomber launching a Long Range Anti-Ship Missile (LRASM), also engaged and heavily damaged the ship. This multi-domain coordinated assault allowed crews to sharpen critical skills in weapons employment and target engagement. The USS Juneau was thoroughly cleaned of hazardous materials before being used as a target, adhering to environmental regulations.

Why It Matters

This sinking exercise during Valiant Shield 2026 is significant because it demonstrates the advanced capabilities and interoperability of the U.S. and its allies in the Indo-Pacific region. Such realistic, live-fire training provides invaluable experience in detecting, tracking, and engaging threats across sea, air, and subsurface domains, honing the lethal precision and coordination essential for high-end maritime operations. By integrating forces from multiple nations, the exercise reinforces the collective readiness to rapidly respond to crises and contingencies, underscoring a commitment to a free and open Indo-Pacific. The use of a decommissioned ship like the USS Juneau allows for testing new technologies and strategies in a way that simulators cannot fully replicate, enhancing overall combined and joint force readiness.

Geographic Location

• Philippine Sea, more than 200 nautical miles off the coast of Guam (sinking exercise of USS Juneau (LPD-10))
• Mariana Islands Range Complex, Pacific Ocean (sinking exercise of USS Juneau (LPD-10))
• Guam, Mariana Islands, United States (location of Exercise Valiant Shield activities)
• Northern Mariana Islands, United States (location of Exercise Valiant Shield activities)
• Japan (location of Exercise Valiant Shield activities)