US Navy selects USS Colorado as first nuclear submarine for AUKUS rotations in Australia from 2027.

The United States, Australia, and the United Kingdom designated the USS Colorado (SSN 788) as the inaugural attack submarine assigned to Submarine Rotational Force-West (SRF-West), with operations scheduled to start at HMAS Stirling in late 2027. Announced on October 26, 2026, under AUKUS Pillar I, the milestone marks the operational rollout of allied nuclear submarine rotations in Western Australia. The assignment leads an expanding force framework planned to host up to four U.S. Virginia-class and one British Astute-class submarine to accelerate Australia's sovereign sustainment infrastructure and strengthen regional maritime deterrence.

The U.S., the UK, and Australia designated the USS Colorado (SSN 788), a Virginia-class nuclear-powered attack submarine, as the first vessel to join AUKUS Submarine Rotational Force-West at HMAS Stirling in Australia in late 2027. (Picture source: US Navy)

On October 26, 2026, the United States, Australia, and the United Kingdom designated the USS Colorado (SSN 788), a Virginia Block III nuclear-powered attack submarine, as the first vessel assigned to Submarine Rotational Force-West (SRF-West), scheduled to begin operations at HMAS Stirling, Western Australia, in late 2027. U.S. Secretary of War Pete Hegseth, Australian Defence Minister Richard Marles, and British Defence Secretary Wes Streeting confirmed that the force will eventually accommodate up to four American Virginia-class submarines and one British Astute-class submarine. Commissioned on March 17, 2018, the USS Colorado operated from Groton, Connecticut, until 2024 and is now based at Pearl Harbor, Hawaii, where it arrived on September 23, 2026.

The submarine will undergo maintenance at HMAS Stirling in October 2026, resume its deployment, and return in late 2027. Located on Garden Island, 60 km south of Perth, the base will support allied submarine rotations before Australia receives its first three sovereign Virginia-class submarines in the early 2030s and Australian-built SSN-AUKUS submarines in the 2040s. The USS Colorado will remain under U.S. Navy command, without permanent Australian homeporting or transfer of ownership. The USS Colorado measures 114.8 m in length, has a 10.36 m beam, displaces 7,925 tonnes submerged, and uses an S9G pressurized-water nuclear reactor driving a single shaft.

Related topic: Australia confirms enduring access for US Virginia-class submarines at HMAS Stirling naval base under AUKUS

Its submerged speed exceeds 25 knots, compared with 20 knots for Australia's Collins-class, while its hull is 37 m longer and its submerged displacement exceeds that of the Collins-class by 4,525 tonnes. Its Block III configuration incorporates a Large Aperture Bow sonar array and two Virginia Payload Tubes, each accommodating six Tomahawk missiles, replacing the 12 individual vertical-launch cells of earlier submarines. Four 533 mm torpedo tubes accommodate Mk 48 ADCAP heavyweight torpedoes and compatible submarine-launched weapons. Unlike diesel-electric submarines, Virginia-class vessels do not need to snorkel for battery charging, allowing sustained submerged operations constrained primarily by provisions, crew endurance, and maintenance. The USS Colorado can conduct anti-submarine warfare, surface-ship attacks, intelligence collection, special operations support, and conventional land strikes, although its 2027 weapons loadout and operational assignments remain unspecified. 

SRF-West's planned five-submarine complement comprises four American Virginia-class vessels and one British Astute-class vessel, but does not represent five submarines continuously stationed at HMAS Stirling. In 2026, the U.S. Navy reestablished Submarine Squadron 3 to oversee U.S. submarine operations associated with SRF-West, established Naval Support Activity Stirling for personnel and administrative services, and created a Lead Maintenance Activity in Western Australia to coordinate submarine maintenance. These organizations separate operational command, technical maintenance oversight, and logistical support while U.S. and British submarines remain under their respective national commands. U.S. access operates under the bilateral Force Posture Agreement, British participation follows separate arrangements, and Australia retains sovereignty over the installation.

The actual operational contribution will depend on submarine rotation frequency, simultaneous berth occupancy, maintenance turnaround times, and patrol days generated from Western Australia. None of these figures has been specified, preventing the planned five-submarine capacity from being translated into a verified increase in deployed submarine strength. HMAS Stirling's maintenance program has progressed through four submarine maintenance periods since 2024. The USS Hawaii (SSN 776) underwent tender-supported maintenance in August-September 2024 using the USS Emory S. Land (AS 39), while the USS Vermont (SSN 792) completed the first shore-supported American maintenance period in October-November 2025 without a tender. The Vermont workforce included 19 ASC trainees, two Raytheon and Thales personnel, 22 Australian fleet-support personnel, and eight clearance divers, while 13 Australian sailors served within its 134-person crew, representing 9.7%.

The HMS Anson (S123) followed in February-March 2026 as the first British Astute-class submarine maintained at the installation, involving approximately 100 personnel and Australian-manufactured components. The USS Colorado's October 2026 maintenance includes Australian-made sail scaffolding, replacement of a thin-line towed sonar array, internal repairs, and use of the upgraded Diamantina Pier. Australian personnel will also conduct radiological emergency exercises without transferring radioactive waste ashore. The progression demonstrates the shift from tender-dependent maintenance to locally executed repairs, although labour-hours, repair turnaround times, and independent Australian certification rates remain unquantified. However, HMAS Stirling must accommodate submarines with substantially different dimensions and weapons arrangements.

The Virginia Block III configuration measures 114.8 m and displaces 7,925 tonnes submerged, while Block V submarines fitted with the Virginia Payload Module measure 140.5 m and displace 10,364 tonnes. The 25.7 m hull extension adds four payload tubes carrying up to 28 additional Tomahawk missiles, increasing vertical-launch capacity from 12 to 40 missiles. British Astute-class submarines measure 97 m, displace approximately 7,400 tonnes submerged, and use Rolls-Royce PWR2 reactors, six 533 mm torpedo tubes, Spearfish torpedoes, and tube-launched Tomahawk missiles. These differences subsequently require separate weapons-handling equipment, maintenance procedures, spare-parts inventories, and technical certification arrangements. Berths must accommodate the 43.5 m length difference between an Astute and a Virginia Block V with the payload module, while continuing to support Australia's Collins-class submarines, which measure 77.8 m.

The engineering requirement consequently extends beyond submarine access to hull-specific mooring, crane reach, temporary utilities, sonar maintenance, and equipment handling. Australia's A$8 billion expansion of HMAS Stirling includes four identified infrastructure packages totaling A$1.6714 billion: A$738.1 million for SRF-West Priority Works, A$212.3 million for accommodation, parking, and the Navy Training Systems Centre-West Stage 2, A$74.9 million for early works, and A$646.1 million for exempted facilities. Construction includes submarine berths, dredging, upgraded shore services, a small-boat pontoon, modifications to the Explosive Ordnance Loading Wharf, a Controlled Industrial Facility, a Radiological Controls Technical Field Office, a dedicated power station, and a pure-water processing plant.

Preliminary construction began in 2024, followed by main works in August 2025. The schedule establishes Initial Operating Support in 2027, Full Operating Support by the end of 2030, and sovereign readiness before Australia's first Virginia-class acquisition in the early 2030s. Longer-term facilities are intended to support at least half of Australia's sovereign nuclear-powered submarine fleet by the early 2040s. Australia has more than 200 Royal Australian Navy personnel undertaking nuclear-submarine training and postings in the U.S., alongside more than 220 Australian industrial personnel training at Pearl Harbor Naval Shipyard. More than ten industrial trainees have returned since December 2025, although the number independently qualified to certify nuclear-submarine maintenance remains unspecified.

In May 2026, Lockheed Martin Australia became the preferred Combat System Integration Partner for Australia's Virginia-class fleet, with 100 additional jobs anticipated and an initial two-year services contract planned. Its responsibilities include combat system integration, testing, upgrades, repair, and sustainment, complementing existing American-Australian armament cooperation. Australia intends to acquire three Virginia-class submarines from the early 2030s, potentially followed by additional vessels, before introducing Australian-built SSN-AUKUS submarines in the early 2040s. The broader submarine enterprise is projected to generate 20,000 direct jobs over 30 years, but its operational readiness will depend on qualified crews, engineering authorities, maintenance certifiers, and industrial personnel. 

For China, SRF-West's principal operational consequence is the potential increase in Western submarine patrol availability across the eastern Indian Ocean and maritime routes connecting the Pacific through the Strait of Malacca, Lombok Strait, and other Indonesian passages. HMAS Stirling provides American and British submarines with a maintenance location on Australia's Indian Ocean coast, potentially reducing non-operational transit time for vessels patrolling the region. More frequent allied patrols could complicate Chinese submarine detection and surface-ship escort requirements.

This could become particularly significant if the People's Liberation Army Navy must distribute Type 054A and Type 054B frigates, Type 052D destroyers, Y-8Q maritime patrol aircraft, and other anti-submarine assets across additional maritime approaches. However, the planned five-submarine rotational complement does not establish five additional submarines continuously at sea, and no China-specific missions have been announced. The measurable military effect will depend on annual patrol days, maintenance turnaround times, simultaneous submarine availability, and whether Chinese naval forces subsequently alter surveillance coverage or escort allocations.

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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, South Korea, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.