USS Colorado Will Start Regular Australian Submarine Rotations in Late 2027

The 7,800-ton USS Colorado will become the first U.S. nuclear-powered submarine assigned to a regular allied rotation through Australia beginning in late 2027. Under the joint U.S., Australian and British announcement, the Virginia-class attack submarine will operate from HMAS Stirling in Western Australia without being permanently based there.

That distinction defines the new force. American submarines have visited Australia before, but the planned Submarine Rotational Force-West establishes a recurring U.S. presence with assigned boats, supporting infrastructure and a trained Australian workforce. The force is eventually expected to accommodate rotations of as many as four U.S. fast-attack submarines and one British fast-attack submarine.

For readers watching China’s military expansion, the selection puts a specific submarine and start date behind plans for a regular American undersea presence in Australia. The three partner governments present the arrangement as a way to strengthen regional deterrence. It also gives allied submarines another location for maintenance and support in the Indo-Pacific, rather than relying solely on facilities farther away.

Colorado moves the plan from visits to rotation

USS Colorado, designated SSN 788, is 115 meters, or 380 feet, long and was commissioned in March 2018. The nuclear-powered submarine carries conventional weapons, including torpedoes and land-attack missiles, and is designed for undersea warfare, surveillance and attacks on land targets.

Its assignment follows a series of maintenance visits intended to prepare HMAS Stirling for the rotational force. Colorado arrived at the base on October 27, 2026, for a planned monthlong maintenance period. More than 30 trained and certified Australian civilian technicians were scheduled to perform routine work on a Virginia-class submarine there for the first time, alongside U.S. specialists.

The maintenance period was the fourth conducted in Western Australia since the AUKUS partnership was established and the third involving submarine maintenance there within 12 months. Earlier work had already exercised locally supplied equipment and pier services, including a mobile pure-water plant, high-pressure air equipment, a dehumidifier and a safety walkway used to reach parts of a submarine’s sail.

Those systems illustrate why hosting nuclear-powered submarines involves more than providing berth space. A rotation requires qualified technicians, controlled maintenance processes, suitable utilities, documented safety procedures and regulatory oversight. The propulsion plant is nuclear even though the submarine’s weapons are conventional, so Australia must build a nuclear-stewardship system alongside its physical support capacity.

A training platform for Australia’s own fleet

The rotational force is also intended to prepare Australia to own, operate, maintain and regulate its planned nuclear-powered submarines. Working on visiting American and British boats gives Australian personnel practical experience before the country fields that sovereign capability.

This creates a demanding systems-integration task. Infrastructure, workforce certification, supply chains and national regulation must mature together; progress in only one area cannot support a safe and reliable submarine operation. Regular rotations provide repeated opportunities to validate those elements under operating conditions, rather than attempting to assemble the entire support system when Australia’s own submarines arrive.

The undertaking carries a substantial public cost. Government forecasts cited for Australia’s wider submarine program put the potential expense as high as US$235 billion over 30 years. The value of the rotational phase will therefore depend partly on whether it produces durable Australian skills and facilities, rather than functioning only as access for visiting allied vessels.

Nuclear governance remains another requirement. The three countries say the rotations will comply with the Treaty on the Non-Proliferation of Nuclear Weapons, while Australia will continue to observe the South Pacific Nuclear Free Zone Treaty, also known as the Treaty of Rarotonga. Safeguards and verification arrangements are particularly important because naval nuclear propulsion involves nuclear material without making the submarines nuclear-armed.

Colorado’s planned return in late 2027 is consequently both an operational milestone and a capacity test. The submarine will begin the first regular U.S. rotation at HMAS Stirling, but the more consequential measure will be whether Australia can safely support a force that may grow to four American boats and one British boat each rotating through the base rather than permanently residing there.

By Thomas Caldwell — AMI’s senior editor for mechanical and mobility engineering, covering vehicle electronics, systems integration, electrification, chassis systems, propulsion, and safety policy.