Canadian submarine HMCS Corner Brook sinks USS Mobile Bay cruiser with Mk 48 torpedo during RIMPAC 2026.

On July 12, 2026, the Canadian submarine HMCS Corner Brook fired a Mk 48 Mod 7AT heavyweight torpedo to deliver the decisive strike against the decommissioned Ticonderoga-class cruiser USS Mobile Bay during RIMPAC 2026 north of Kauai, Hawaii. The multi-axis exercise integrated strike weapons across land, air, surface, and undersea forces to test joint targeting against a major surface combatant in a high-depth maritime environment. The strike verified the operational recovery of Canada's submarine force, establishing an active target engagement chain after a 14-year period removed from normal operational cycles.

During the SINKEX event, multinational coalition forces fired a combination of M142 HIMARS rockets, Type 12 anti-ship missiles, AGM-158C LRASMs, Spike NLOS missiles, and heavyweight torpedoes against the decommissioned hull in water 4,570 meters deep. HMCS Corner Brook generated the final loss of buoyancy using a wire-guided Mk 48 Mod 7AT torpedo following a C$695 million refit and modernization program completed on April 2, 2025.

Related topic: Canadian Navy declares Victoria-class submarine HMCS Corner Brook ready for Indo-Pacific deployment

During RIMPAC 2026, the HMCS Corner Brook fired a Mk 48 Mod 7AT heavyweight torpedo that delivered the final strike against the decommissioned Ticonderoga-class guided-missile cruiser USS Mobile Bay. (Picture source: US Navy)

On July 12, 2026, the Canadian submarine HMCS Corner Brook fired a Mk 48 Mod 7AT heavyweight torpedo that delivered the final strike against the decommissioned Ticonderoga-class guided-missile cruiser USS Mobile Bay during a multinational sinking exercise north of Kauai, Hawaii. The attack concluded a coordinated sequence involving land-based anti-ship missiles, fighter jets, attack helicopters, surface forces and submarines. The USS Mobile Bay sank in water about 4,570 meters deep, more than 50 nautical miles from Kauai’s northern coast, after sustaining multiple weapon impacts before the Canadian torpedo caused the final loss of buoyancy.

The event marked the first participation of a Canadian submarine in RIMPAC since the HMCS Victoria attended in 2014 and the first major multinational deployment by the HMCS Corner Brook after it returned to full operational service on April 2, 2025. The exercise therefore tested whether Canada could again generate a complete submarine engagement chain, from passive detection and target classification to weapon launch, after a 14-year period in which the boat had been removed from normal operational cycles. RIMPAC 2026 ran from June 24 to July 31 in and around the Hawaiian Islands and involved 31 countries, 36 surface ships, five submarines, 15 national land forces, more than 206 aircraft and about 25,000 personnel.

The USS Mobile Bay SINKEX combined weapons with substantially different launch ranges, flight profiles, terminal guidance methods, and warhead effects. Personnel from the Kentucky National Guard’s 1st Battalion, 623rd Field Artillery used the M142 HIMARS, while the Japan Ground Self-Defense Force’s 8th Surface-to-Surface Missile Regiment fired Type 12 anti-ship missiles. U.S. Navy F/A-18E/F Super Hornets carried AGM-158C Long-Range Anti-Ship Missiles. U.S. Army AH-64 Apache helicopters fired Spike non-line-of-sight missiles, adding a lower-altitude, shorter-range attack axis suitable for engaging exposed topside structures, sensors and machinery spaces. The Canadian torpedo detonated against the hull below the waterline and produced damage that cannot be replicated by above-water missile impacts. 

The USS Mobile Bay, hull number CG-53, entered U.S. Navy service on February 21, 1987, as the seventh operational Ticonderoga-class guided-missile cruiser. The ship measured 173 meters in length, 16.8 meters in beam, and displaced close to 9,800 tonnes at full load, for a maximum speed above 30 knots. Its combat capability centered on the Aegis combat system and AN/SPY-1 phased-array radar, supported by AN/SPG-62 fire control radars, surface search radars, and the AN/SQQ-89 anti-submarine warfare suite. Two Mk 41 Vertical Launching Systems provided 122 missile cells that could carry combinations of SM-2, SM-3, ESSM, Tomahawk, and RUM-139 VL-ASROC weapons, giving the cruiser the ability to conduct air defense, ballistic missile defense, land attack, and anti-submarine warfare.

The ship also carried eight RGM-84 Harpoon anti-ship missiles, two 127 mm Mk 45 guns, two Phalanx close-in weapon systems, two triple 324 mm torpedo launchers, and two MH-60 Seahawk helicopters. During Operation Desert Storm, USS Mobile Bay launched 22 Tomahawk missiles and served as the air warfare commander for a four-carrier force, while later assignments included Operation Southern Watch, Operation Iraqi Freedom and repeated carrier strike group deployments in the Western Pacific and Middle East. Its decommissioning on August 10, 2023 reflected the wider retirement of the Ticonderoga class, whose Spruance-derived hull, crew requirement of about 330 personnel, corrosion burden and limited electrical and weight margins had become increasingly costly to sustain.

For its part, the HMCS Corner Brook is a Victoria-class diesel-electric submarine that entered service with the British Navy as HMS Ursula on May 8, 1992. Canada acquired the four Upholder-class boats in 1998 under an eight-year lease valued at US$427 million, with a further US$98 million for conversion to Canadian standards, and commissioned the former Ursula as HMCS Corner Brook on June 29, 2003. The submarine is 70.3 meters long, 7.6 meters wide and about 5.5 meters in draught, with a surfaced displacement of about 2,220 tonnes and a submerged displacement between 2,439 and 2,495 tonnes. Its propulsion system combines two Paxman diesel generators, batteries, an electric motor, a single shaft and a seven-bladed fixed-pitch propeller.

Maximum speed is about 12 knots surfaced and more than 20 knots submerged, although high submerged speed rapidly consumes battery capacity and cannot be sustained for the periods available to a nuclear-powered attack submarine. Reported range reaches 10,000 nautical miles at economical speed, test depth is about 200 meters, and crew size varies between 49 and 59 personnel depending on the operating configuration. The class does not use air-independent propulsion (AIP), meaning it must periodically raise a snorkel to run its diesel generators and recharge batteries. Its operational advantage instead lies in low acoustic output at low speed, a comparatively small hull and the ability to remain stationary or maneuver slowly in confined waters while using passive sensors to build a firing solution.

In terms of armaments, the HMCS Corner Brook carries six 533 mm torpedo tubes and can embark up to 18 heavyweight torpedoes. In British service, the class used Tigerfish torpedoes and UGM-84 Sub-Harpoon missiles and retained a minelaying capability, but Canada removed the missile and mine functions and modified the boats to fire the U.S. Mk 48 torpedo. The Canadian conversion incorporated the Librascope Submarine fire control system and equipment derived from the retired Oberon-class, initially enabling employment of the Mk 48 Mod 4. In 2014, Canada purchased 12 upgrade kits to support the Mk 48 Mod 7AT across the fleet. The Mod 7AT is intended for use against both submarines and surface ships in acoustically difficult waters, where temperature layers, salinity changes, bottom reverberation, merchant traffic and decoys can generate false contacts or interfere with terminal homing.

Before firing on USS Mobile Bay, the submarine had to establish target bearing, course, speed and range, calculate an intercept point, select torpedo search parameters and verify that no friendly ship or submarine had entered the weapon danger area. After launch, the weapon remained connected to the submarine by guidance wire, allowing the command team to update the track before the torpedo shifted to autonomous terminal search. The submarine’s sensor and electronic warfare fit is central to its ability to approach a target without revealing its position. The HMCS Corner Brook retains the Type 1007 radar, CK035 electro-optical search periscope and CH085 optronic attack periscope, while its sonar suite includes the Type 2007 array and Type 2046 towed array integrated with the Canadian Towed Array Sonar System.

A towed array positions passive hydrophones behind the submarine and away from part of the machinery and flow noise generated by the hull, improving detection of low-frequency contacts when the boat is operating at suitable speed and depth. Canadian modifications also include the AR 900 electronic support measures system, which detects and classifies radar emissions without requiring the submarine to transmit, and two SSE launchers for deploying acoustic decoys against incoming torpedoes. Before RIMPAC 2026, the HMCS Corner Brook also received a modern electronic warfare system to improve detection and identification of nearby ships and emitters, reducing the time required to expose a periscope or radar mast. Elastomeric acoustic tiles fitted to the hull reduce radiated machinery noise and can diminish the return produced by active sonar, although their effectiveness depends on tile condition, frequency, aspect and water conditions.

These upgrades preserve a credible surveillance, intelligence collection, anti-submarine and torpedo attack capability, but modernization is constrained by the submarine’s available electrical power, cooling capacity, cable routes, internal volume and weight margins. More importantly, the RIMPAC deployment followed a 14-year repair and modernization cycle that began when the HMCS Corner Brook struck the seabed in Nootka Sound off Vancouver Island on June 4, 2011. The submarine was travelling at about 5.9 knots in water 45 meters deep when the collision opened a hole approximately two meters long in the bow and caused minor injuries to two crew members. The boat surfaced and returned to Esquimalt under its own power; a board of inquiry later attributed the grounding to human error, and the damage removed it from operational service.

The HMCS Corner Brook then entered an Extended Docking Work Period in 2014 that was initially scheduled to end in 2017, but the work expanded to include structural repair, deep maintenance, equipment replacement and life-extension activity. On April 1, 2019, a fire occurred while the submarine remained in dry dock at CFB Esquimalt. In March 2020, a ballast tank test caused an overpressurization event after compressed air was used too rapidly to empty the tanks, producing another rupture and further delaying the return to sea. Immediate repairs associated with the grounding cost about C$20 million, while the wider maintenance, modernization and life-extension package reached about C$695 million before the submarine finally returned to full operational capability in April 2025.

The total period out of normal service therefore exceeded the original operational career of HMS Ursula, which lasted from May 1992 to October 1994, and demonstrated how a single accident can remove a submarine for more than a decade. At the time of RIMPAC 2026, HMCS Corner Brook was the only operational submarine in Canada’s four-boat Victoria-class fleet, but it still required crew training, ammunition handling, defect correction, scheduled maintenance and transit time between Esquimalt and operating areas in the central Pacific. A four-submarine fleet normally needs at least one boat in deep maintenance, one in shorter maintenance or work-up, one available for training and one deployable, leaving no reserve when a major refit overruns or an unexpected defect appears.

Canada had not sent a submarine to RIMPAC since HMCS Victoria participated in 2014, and a planned deployment in 2020 was cancelled during the COVID-19 pandemic. The July 2026 firing therefore restored a Canadian undersea contribution to a major multinational exercise but did not demonstrate the ability to sustain simultaneous Pacific, Atlantic and Arctic submarine tasking. Canada’s plan to acquire up to 12 Type 212CD submarines would increase the number of deployable hulls, but the operational effect will depend on procurement timing, infrastructure at Esquimalt and Halifax, crew generation, weapons integration, maintenance capacity and the transition period between the Victoria class and its replacement.

Written by Jérôme Brahy

Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.

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