Australia, the United States and the United Kingdom have marked another important step in Australia’s preparations for the establishment of Submarine Rotational Force‑West (SRF‑West), with the arrival of USS Colorado at HMAS Stirling for the next US Submarine Maintenance Period.

The USS Colorado’s visit will demonstrate Australia’s growing ability to sustain US and UK nuclear-powered submarines, while continuing to build the workforce, infrastructure, and technical expertise to operate Australia's sovereign nuclear‑powered submarine capability.

The USS Colorado holds particular significance as it will return to HMAS Stirling in late 2027 as the first submarine to begin rotations under SRF-West.

As part of this maintenance period, fully trained and qualified Australian personnel are conducting work on an operational US Virginia-class submarine, using Australian-designed maintenance infrastructure and equipment, and upgraded port facilities.

This maintenance period has been designed to further strengthen the skills, systems, and supply chains required to support the routine sustainment of nuclear-powered submarines in Australia. It demonstrates the scale, complexity and sophistication of the maintenance activities Australian personnel are capable of undertaking.

Key activities to be undertaken during the US Submarine Maintenance Period include:

• The installation of an Australian-made sail maintenance scaffolding, also known as a ‘racetrack’, which will sit around the submarine during its time at HMAS Stirling  –  giving workers safe and rapid access to carry out submarine maintenance work
• Personnel from Australia, the UK and the US working side-by-side to conduct off-hull capability demonstrations using specialised training equipment and locally produced submarine components
• Australian personnel conducting in-hull maintenance work, including replacing the thin line towed array and ship repairs
• Use of the newly upgraded Diamantina Pier at HMAS Stirling, demonstrating Australia’s increased readiness to sustain conventionally-armed nuclear‑powered submarines.
• Australian personnel (supported by US personnel) conducting simulated radiological scenarios that exercise radiation safety practices and procedures, with no radioactive waste being transferred ashore.

These scenarios have been designed to simulate elements of the capability that will be in place at HMAS Stirling to support the initial scope of maintenance activities from 2027.

All activities under the Submarine Maintenance Period continue to be undertaken in full accordance with the non-proliferation and safeguards obligations of Australia, the US and the UK.

Under the AUKUS pathway, UK and US nuclear-powered submarines have conducted increasingly regular and extended visits to HMAS Stirling, with each visit and maintenance period building on the achievements of the last, as follows:

• US Submarine Tendered Maintenance Period (August-September 2024): The first-ever joint maintenance period conducted on a US nuclear submarine in Australia, delivered on the USS Hawaii (SSN-776) and supported by the USS Emory S. Land (AS-39)
• US Submarine Maintenance Period 25 (October-November 2025): A historic milestone where the USS Vermont (SSN‑792) was successfully serviced without a support ship, relying on shoreside facilities and a blended US and Australian workforce for the first time
• UK Submarine Maintenance Period 26 (February-March 2026): The first ever maintenance activity conducted in Australia on a UK Royal Navy Astute-class submarine, HMS Anson (S123) which successfully integrated local Australian-made components and systems

SRF-West is on track to commence in 2027, which will see Australia build the workforce, infrastructure and operational expertise required to support AUKUS, strengthen cooperation with Australia’s AUKUS partners, and contribute to regional security, stability and deterrence in the Indo-Pacific.

Further information on SRF-West is available at https://www.asa.gov.au/

Quotes attributable to Director General Australian Submarine Agency, Vice Admiral Jonathan Mead, AO RAN:

“Since the previous maintenance activity on a US Virginia-class submarine in late 2025, Australia has worked with our AUKUS partners to grow our workforce, upgrade infrastructure at HMAS Stirling, strengthen regulatory frameworks, and welcome the first US personnel to Western Australia.

“This is the fourth maintenance period since 2024. Each visit sees a significant growth in the number of Australians supporting maintenance on visiting boats, from local industry to Navy divers. It is genuinely exciting to see how far we’ve come as a country in such a short time.

“This SMP is helping develop the skilled workforce needed to support Australia's future submarine capability. It will create opportunities for Australian industry, supporting local jobs, businesses and economic growth.

“This port visit doesn’t just support routine maintenance efforts for a US submarine. It demonstrates Australian sovereign industrial capability and the progress being made towards SRF-West and the delivery of AUKUS.”

Quotes attributable to Chief of Navy, Vice Admiral Matt Buckley AM CSC RAN:

"By regularly rotating through HMAS Stirling, US and UK nuclear-powered submarines will strengthen our collective capability, increasing Navy-to-Navy cooperation and contributing to a secure and stable Indo-Pacific.

“The presence of US and UK nuclear-powered submarines at HMAS Stirling for maintenance and shore support activities provides our Royal Australian Navy personnel with invaluable hands-on experience and the skills and expertise needed to support and sustain Australia’s future conventionally armed, nuclear-powered submarine capability.”

Media note

Media can access imagery and vision of the arrival of US Colorado at HMAS Stirling at http://images.defence.gov.au/S20263067