USS Colorado will be the first US attack submarine to rotate through Western Australia under AUKUS

The United States, Australia and Britain have picked the Virginia-class attack submarine USS Colorado as the first American boat to be assigned to Submarine Rotational Force-West, the AUKUS arrangement that will base nuclear-powered submarines on rotation at HMAS Stirling, near Perth. The rotation is due to begin in late 2027.

The designation was announced on 26 October in Washington, 27 October in Australia, in a joint statement by US Secretary of War Pete Hegseth, Australian Deputy Prime Minister and Defence Minister Richard Marles and British Defence Secretary Wes Streeting. The three governments called the choice a significant milestone for the first pillar of AUKUS, which covers submarines, and a step towards stronger collective deterrence in the Pacific.

According to the statement, the rotational force is expected to host up to four US fast-attack submarines and one British boat at the Royal Australian Navy base. The announcement came ahead of a US submarine maintenance period at Stirling that is due to start later this week, which the partners said would further show Australia's growing ability to sustain American and British nuclear-powered submarines.

The partners framed the force as a training ground for Australia's own fleet. They said it would speed up Australian readiness to own, operate, maintain and regulate a sovereign, conventionally armed, nuclear-powered submarine capability, and would widen maintenance options and support infrastructure for AUKUS submarine deployments in the region.

The statement said the force was set up at Australia's invitation and would operate under existing agreements among the three countries, including the US-Australia Force Posture Agreement. It also said the activity would respect the partners' obligations under the Nuclear Non-Proliferation Treaty and Australia's commitments under the South Pacific Nuclear Free Zone Treaty, known as the Treaty of Rarotonga.

USS Colorado was commissioned on 17 March 2018 and is the 15th boat of the Virginia class, IANS reported. It is the fifth built to the redesigned Block III standard. In June, Pearl Harbor Naval Shipyard said it had finished a scheduled maintenance period on the boat 29 days ahead of plan, USNI News reported.

Groundwork for the force has been building through 2026. In June the US Navy re-established Submarine Squadron 3 at Stirling to handle maintenance, logistics and operational support for rotating US and British submarines, after setting up a new Naval Support Activity Stirling on 30 May to serve American personnel and their families, USNI News reported. Pearl Harbor Naval Shipyard also planned a maintenance and logistics detachment in Western Australia from mid-2026.

Australian crews and workers are already training on American boats. IANS, citing the June announcement, said more than 200 Royal Australian Navy personnel were training or posted in the United States and more than 220 Australian industry workers were gaining experience at Pearl Harbor Naval Shipyard. The British submarine HMS Anson carried out a maintenance period at Stirling earlier this year before it was recalled to Britain, according to USNI News.

Under its AUKUS plan, Australia intends to buy three in-service Virginia-class submarines from the United States and to acquire five SSN-AUKUS boats, USNI News reported.

For the wider Indo-Pacific, the partners present the rotation as a way to keep more US and British attack submarines supported in the region rather than sending them home for upkeep, as they look to strengthen deterrence in the Pacific. The joint statement did not say how long USS Colorado will stay in Western Australia or which boats will follow it.