Submarine sinks American cruiser in Pacific Exercise

The decommissioned US Navy guided-missile cruiser USS Mobile Bay has been sunk during a live-fire exercise at RIMPAC 2026 in the Pacific, the US Navy stated.

Ships and aircraft taking part in the Rim of the Pacific exercise conducted a planned sinking exercise, sending the former Ticonderoga-class cruiser to the bottom on 12 July. A second target, the decommissioned amphibious assault ship USS Peleliu, was sunk on 17 July. According to the US Navy, both ships were sunk in waters around 15,000 feet deep, more than 50 nautical miles off the northern coast of Kauai.

A striking image of the exercise was captured through the periscope of the Royal Canadian Navy Victoria-class submarine HMCS Corner Brook, showing Mobile Bay settling into the Pacific.

According to reporting on the exercise, Corner Brook fired a Mk 48 heavyweight torpedo to deliver the decisive strike against the cruiser, in what was the first participation of a Canadian submarine in RIMPAC since 2014.

The engagement marked a milestone for Canada’s submarine force. Corner Brook returned to full operational service in 2025 after a lengthy period out of the normal operational cycle, and the strike tested the boat’s ability to generate a complete engagement chain, from detection and classification through to weapon launch against a major surface combatant.

A sinking exercise, or SINKEX, uses a decommissioned warship as a full-size target for live weapons, allowing crews to fire against a real hull and giving engineers insight into how modern vessels absorb damage and sink. The Mobile Bay event drew in a range of weapons from across the coalition. According to reporting on the exercise, coalition forces fired HIMARS rockets, anti-ship missiles including the Type 12 and the long-range LRASM, Spike missiles and heavyweight torpedoes against the hull. US Army AH-64 Apache attack helicopters engaged the cruiser with Spike NLOS missiles.

USS Mobile Bay was commissioned in February 1987 and served for more than 36 years before decommissioning in August 2023. Over three decades of service the cruiser supported Operations Desert Shield, Desert Storm and Iraqi Freedom, firing Tomahawk cruise missiles in two wars, and delivered humanitarian assistance following the 1991 Mount Pinatubo eruption in the Philippines.

RIMPAC is the world’s largest international maritime exercise, held around the Hawaiian Islands. The 2026 edition ran from 24 June to 31 July and involved 31 nations, 36 surface ships, five submarines, 15 national land forces, more than 200 aircraft and around 25,000 personnel. First held in 1971, RIMPAC 2026 is the 30th exercise in the series, and its live-fire sinking exercises give participating navies a rare chance to observe how modern weapons perform against a real warship.