US Navy submarine crisis worsens as first Improved Los Angeles-class submarine USS San Juan retires.

On August 6, 2026, the U.S. Navy decommissioned the fast-attack submarine USS San Juan (SSN-751) at the U.S. Naval Undersea Museum in Keyport, Washington, following 38 years of operational service. As the first Improved Los Angeles-class (688i) submarine, its retirement marks the operational drawdown of the platform that introduced retractable bow diving planes, reinforced Arctic sail structures, and integrated vertical launch missile capabilities. The event reflects broader operational force-structure challenges as legacy attack submarines retire at a pace exceeding new Virginia-class fleet deliveries.

Commissioned on August 6, 1988, and built by General Dynamics Electric Boat, USS San Juan measured 110.3 meters in length with a 6,197-long-ton submerged displacement, powered by an S6G nuclear reactor supplying 33,500 shaft horsepower. Armed with four 533 mm torpedo tubes and 12 Tomahawk vertical launch cells, the boat completed its final 37,600-nautical-mile deployment in June 2023 before transitioning into stand-down ahead of its final decommissioning.

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The USS San Juan was the prototype of the Improved Los Angeles-class, introducing Arctic, stealth, and combat system upgrades that became the standard for every subsequent 688i attack submarine and influenced key design priorities later carried over into the Virginia-class. (Picture source: US Navy)

On August 6, 2026, the U.S. Navy decommissioned the USS San Juan (SSN-751) at the U.S. Naval Undersea Museum in Keyport, Washington, exactly 38 years after the submarine was commissioned on August 6, 1988. The retirement removed the first Improved Los Angeles-class nuclear-powered attack submarine from the fleet and ended the career of the boat that established the 688i configuration subsequently used from SSN-752 through SSN-773. USS San Juan completed its final operational deployment on June 6, 2023, after five-and-a-half months in the U.S. Sixth Fleet area, departed Naval Submarine Base New London for the Pacific on August 21, 2023, reached Naval Base Kitsap-Bremerton on September 20, and entered Reserve, Stand Down status on August 12, 2024.

The timing of the retirement is operationally significant because the U.S. Navy is now removing Los Angeles-class submarines at a rate that exceeds Virginia-class deliveries, with the U.S. attack submarine (SSN) inventory projected to decline from roughly 49 to 50 boats in 2025 toward 46 to 47 near 2030, compared with a long-term requirement of 66 SSNs. General Dynamics Electric Boat received the contract for the USS San Juan on November 30, 1982. The keel was laid at Groton, Connecticut, on August 9, 1985; the submarine was launched on December 6, 1986, and commissioning followed on August 6, 1988, under Cmdr. Charles Young.

By then, the U.S. Navy had already divided the Los Angeles-class into three production groups: 31 Flight I submarines from USS Los Angeles (SSN-688) through USS Providence (SSN-718), eight Flight II submarines from USS Pittsburgh (SSN-719) through USS Newport News (SSN-750), and the final 23 Flight III boats from USS San Juan (SSN-751) through USS Cheyenne (SSN-773). Flight II had introduced a separate battery of 12 vertical launch tubes for Tomahawk missiles, allowing cruise missiles to be fired without using the four bow torpedo tubes, but Flight III (also known as 688i or Improved Los Angeles-class) addressed a different set of problems generated by the improving Soviet submarine force. 

The USS San Juan moved the diving planes from the sail to retractable positions on the bow, received a reinforced sail designed to penetrate Arctic ice, incorporated additional noise-reduction measures, added mine-laying capability, and introduced the AN/BSY-1 combat system. The changes were intended to improve the ability to trail quieter Soviet attack submarines, including the Sierra and Akula classes, and to operate beneath the Arctic ice in areas associated with Soviet ballistic missile submarine patrols. That mission requirement explains why the USS San Juan measured 110.3 m long, 10 m in beam, and 9.4 m in draft. Additionally, its displacement was 5,790 long tons in the lighter condition and 6,197 long tons at full displacement. Propulsion came from one General Electric S6G pressurized-water reactor using a D2W core rated at 165 MW thermal.

That reactor supplied steam to two main propulsion turbines producing 33,500 shaft horsepower through a single shaft, while a 325 hp secondary propulsion motor could provide limited movement if the main propulsion system was unavailable. The Los Angeles-class official submerged speed exceeded 25 knots, while higher maximum figures remained classified. The class had an endurance commonly listed at about 90 days, with nuclear propulsion removing fuel endurance as the principal limitation and shifting operational endurance toward food, maintenance, crew, and mission requirements. USS San Juan normally carried 12 officers and 98 enlisted personnel in its listed configuration. The compact internal volume imposed by a 110.3 m hull meant propulsion machinery, reactor systems, sonar processing spaces, torpedo-room storage, command spaces, crew accommodation, and auxiliary systems all had to be contained within two principal watertight compartments, a layout that remained fundamentally rooted in Cold War attack submarine design.

The USS San Juan had four 533 mm, 21-inch torpedo tubes and 12 dedicated vertical launch tubes located forward of the sail. The torpedo tubes could employ Mk 48 ADCAP heavyweight torpedoes for submarine and surface targets, UGM-84 Harpoon anti-ship missiles, Tomahawk missiles when required, and submarine-launched mines including the Mk 67 mobile mine. The last 31 Los Angeles-class submarines, comprising Flight II and Flight III, added the 12-tube Tomahawk vertical launch system to the internal torpedo room load. Therefore, a 688i submarine could begin a deployment with a 12-missile land attack battery already segregated from the weapons needed for anti-submarine warfare, rather than filling part of its torpedo room capacity with cruise missiles. A submarine tasked with strike missions could therefore preserve Mk 48 availability and avoid tying up torpedo tubes during the initial launch sequence.

The arrangement became increasingly relevant after the Cold War because Los Angeles-class boats shifted from an overwhelmingly submarine-hunting mission toward a combination of anti-submarine warfare, anti-surface warfare, intelligence collection and precision land attack. The USS San Juan demonstrated that transition operationally in March 2003 when it launched Tomahawk land attack missiles from the Red Sea in support of Operation Iraqi Freedom. The sensor and acoustic changes introduced by the USS San Juan were equally important because attack submarine effectiveness depends on detecting another submarine before being detected itself. The Flight III boats entered service with the AN/BSY-1 Submarine Advanced Combat System using the AN/BQQ-5E sensor configuration and more capable digital processing than earlier Los Angeles boats.

The wider AN/BQQ-5 family used a spherical bow sonar array containing 1,241 transducers, a conformal hull array with 104 to 156 hydrophones and multiple towed-array options, providing passive and active detection over different frequency bands and geometries. The 688i upgrade added improved electronics and acoustic isolation intended to reduce machinery-generated noise and improve the quality of passive sonar data reaching the processors. Lower self-noise mattered twice: it reduced the acoustic signal available to an adversary while simultaneously allowing the submarine's own hydrophones to detect weaker contacts against a quieter internal background. The bow-plane arrangement also had an acoustic and hydrodynamic role in addition to its Arctic function.

Removing large diving planes from the sail improved flow around the upper hull and allowed the planes to be retracted when they were not required, while the strengthened sail could withstand ice-breaking loads. The USS San Juan validated the Arctic configuration in 1993 when it conducted the first through-ice surfacing by a 688i submarine. The result was a submarine designed to operate not only in the open Atlantic or Pacific but also beneath Arctic ice where access routes, acoustic propagation, and the inability to surface freely make submarine operations substantially more demanding. The USS San Juan then operated repeatedly in the Atlantic, Mediterranean, North Atlantic, Arctic, and Middle East, including deployments to the U.S. Fifth and Sixth Fleet areas.

Its March 2003 Tomahawk launches from the Red Sea were followed by continued deployments involving Bahrain, Jebel Ali in the United Arab Emirates, Souda Bay in Greece, Rota in Spain, Lisbon in Portugal, Faslane in Scotland, Bergen in Norway, Limassol in Cyprus and Icelandic waters. In November 2009, USS San Juan reached Simon's Town and conducted at-sea activity with the South African Navy. In September 2020, it participated in Exercise Black Widow, providing both an attack submarine target and an operational participant in a multi-unit anti-submarine warfare scenario. In 2021, it took part in Dynamic Manta before operating again through the Mediterranean and North Atlantic. Its final deployment began on December 21, 2022, and ended at New London on June 6, 2023.

During that deployment, the submarine covered nearly 37,600 nautical miles, or 69,635 km, made a 13-day stop at Rota in March, visited Limassol from April 3 to April 7, conducted personnel transfers at Gibraltar on April 18 and off Iceland on April 26, and operated in the High North. Interestingly, thirty-six sailors qualified in submarine warfare during the deployment, while six crew members became fathers while underway. Its 38-year career was sustained by substantial maintenance expenditure and also included incidents that affected hull and operational availability. On March 19, 1998, USS San Juan collided while submerged with the surfaced Ohio-class ballistic missile submarine USS Kentucky (SSBN-737) south of Long Island. The USS San Juan suffered damage to the forward ballast tank, while the USS Kentucky sustained rudder damage; neither crew suffered casualties, and both submarines retained sufficient capability to return safely.

On March 13, 2007, contact with the USS San Juan was lost during operations associated with the USS Enterprise Carrier Strike Group, while a red flare had been observed in the projected area of the submarine. The combination triggered a search-and-rescue effort until communications were re-established during the early hours of March 14 and the boat confirmed that it had not suffered an emergency. The most consequential maintenance event came on April 8, 2010, when the USS San Juan entered Portsmouth Naval Shipyard for an Engineered Overhaul. It left dry dock on August 4, 2011, one day ahead of schedule, and returned to Naval Submarine Base New London on February 10, 2012. That overhaul generated more than another decade of useful operating time, including several European deployments, but it also illustrates the maintenance model that is becoming increasingly expensive to repeat on the surviving 688i fleet.

As hulls move beyond 30 to 35 years of service, continued operation can require reactor work, piping replacement, propulsion maintenance, sonar modernization, electrical renewal and structural preservation, all drawing on nuclear-certified labor that is also needed for Virginia-class and Columbia-class construction. The 688i also provides a clear technological bridge between the original Los Angeles design and the Virginia class. The USS San Juan introduced or consolidated several priorities that remain central to current U.S. attack submarines: reduced acoustic signature, integrated digital combat management, Arctic operations, dedicated conventional land attack capability, and the ability to perform anti-submarine, anti-surface, strike, and intelligence missions with the same hull. Virginia-class submarines retain those functions but change how they are implemented.

The AN/BYG-1 combat architecture uses commercial processor insertion and modular software to allow more frequent upgrades than the AN/BSY-1. Later Virginia boats use the Large Aperture Bow passive sonar array rather than the traditional spherical bow array, while payload architecture has evolved from 12 individual Tomahawk vertical launch tubes on early Virginias to two Virginia Payload Tubes, with Block V adding the Virginia Payload Module for additional missile capacity. Virginia also incorporates an internal lock-out chamber for special operations forces, reflecting a mission that required more external adaptation on older boats. The largest change concerns the nuclear plant. Virginia-class reactor cores are intended to last for the planned service life of the submarine, avoiding the mid-life reactor refueling requirement that can remove older submarines from the fleet for years.

From a fleet management perspective, this is as important as individual improvements in sonar or payload capacity because an SSN that spends less of its service life in deep maintenance generates more deployable days from each hull procured. USS San Juan therefore represents the point at which the Los Angeles class incorporated many of the operational concepts later retained by Virginia without yet solving the maintenance and reactor life problems inherited from the older 688 design. Nevertheless, the force-structure problem created by the retirement of USS San Juan is measurable. The U.S. Navy built 62 Los Angeles-class submarines between 1972 and 1996, more nuclear-powered attack submarines than any other U.S. class, but by 2026 only a fraction of that fleet remained operational.

The surviving force consisted largely of late Flight III boats commissioned between 1988 and 1996, meaning most remaining hulls are now between 30 and 38 years old. That creates an age concentration rather than a gradual retirement curve. During the late Cold War, the US Navy sometimes commissioned four or five Los Angeles-class submarines in a year; roughly four decades later, several boats are consequently reaching economic and nuclear-life limits in the same periods, but Virginia-class production has not reproduced those procurement rates.

The rate required merely to stabilize the U.S. SSN inventory is two Virginia-class submarines per year, while supporting AUKUS transfers and domestic requirements raises the required output above 2.3 boats annually. Actual output has remained near 1.1 to 1.3 submarines per year. If two or three Los Angeles-class submarines retire in a year while only one or slightly more than one Virginia enters service, the fleet loses roughly one to two SSNs annually despite continuing new construction. The cumulative result is visible in force levels: the U.S. attack submarine inventory stood at 52 in 2020, roughly 49 to 50 in 2025, and is projected to fall toward 46 to 47 near 2030, compared with a long-term objective of 66 attack submarines.

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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