By Leonam dos Santos Guimarães*
RIO DE JANEIRO | 25 April 2025 (IDN) — The establishment of the AUKUS trilateral security partnership between Australia, the United Kingdom, and the United States in 2021 constitutes a profound reconfiguration of the strategic landscape in the South China Sea and the broader Indo-Pacific region. Aimed at enhancing Australia’s defense posture through the transfer of critical technologies, notably the acquisition of nuclear-powered submarines, AUKUS introduces new dimensions of deterrence, interoperability, and power projection that recalibrate the regional balance vis-à-vis China’s growing assertiveness.
Foremost among the strategic shifts is the anticipated transformation of Australia’s undersea warfare capabilities. Nuclear-powered submarines (SSNs) differ markedly from their diesel-electric counterparts, providing superior range, endurance, and stealth. These characteristics enable persistent deployments across the Indo-Pacific, particularly within contested areas such as the South China Sea. Australia’s future ability to maintain a continuous and covert undersea presence will significantly complicate Chinese anti-access/area denial (A2/AD) strategies, which rely on limiting the freedom of maneuver of rival forces within the First and Second Island Chains.
AUKUS fortifies the broader U.S.-led security architecture in the Indo-Pacific
Moreover, AUKUS fortifies the broader U.S.-led security architecture in the Indo-Pacific. By integrating Australia more closely into U.S. strategic planning and operations, and eventually into combined submarine patrol patterns, AUKUS enhances collective deterrence efforts. It complements initiatives such as the Quadrilateral Security Dialogue (Quad) and bolsters the Five Eyes intelligence alliance, demonstrating a cohesive and determined response to China’s maritime expansionism.
Notably, the agreement has also provoked geopolitical reactions beyond China. Nations such as Indonesia and Malaysia have expressed concerns about the potential for a regional arms race and the risks to the nuclear non-proliferation regime, despite AUKUS’ strict assurances that the submarines will not be nuclear-armed. Nevertheless, from the perspective of maritime security and freedom of navigation, AUKUS is widely regarded among U.S. allies and partners as a stabilizing factor in counterbalancing unilateral assertions of power.
A critical operational component of AUKUS is the evolving role of HMAS Stirling, located on Garden Island near Perth, Western Australia. HMAS Stirling is poised to become a vital logistical and operational hub for nuclear-powered submarine activities under the aegis of the Submarine Rotational Force – West (SRF-West). Beginning as early as 2027, this initiative envisions a rotational presence of up to four U.S. Virginia-class submarines and one U.K. Astute-class submarine at Stirling, effectively making it a forward operating base for allied SSN activities.
Recent visits, such as that of the USS Minnesota (SSN-783) in early 2025, illustrate the progressive integration of U.S. and Australian naval forces. Port calls have expanded into joint exercises, weapons handling training, and the participation of U.S. crews in the Australian Submarine Command Course, directly contributing to Australia’s future nuclear submarine force proficiency. In preparation for these expanded operations, Stirling is undergoing significant infrastructure upgrades, with an investment exceeding AUD 8 billion, including enhancements to piers, maintenance facilities, and support systems tailored for nuclear-powered vessels.
Strategically, the positioning of a rotational force at Stirling extends U.S. and allied submarine operational reach into the Indian Ocean and deepens deterrence against Chinese maneuvers in the South China Sea. It ensures that allied submarines can sustain high operational tempo missions without relying solely on bases located in Guam or Hawaii, thus mitigating vulnerabilities and providing strategic flexibility.
In conclusion, the AUKUS agreement fundamentally alters the strategic equilibrium in the South China Sea by introducing a formidable and persistent undersea capability aligned with U.S. and allied interests. The transformation of HMAS Stirling into a premier operational hub for nuclear-powered submarines not only strengthens Australia’s defense posture but also solidifies a long-term collective security framework aimed at preserving stability, upholding international law, and deterring coercive behaviors in the Indo-Pacific. As AUKUS advances, the evolving capabilities and partnerships it engenders will continue to reshape the regional strategic environment in enduring and consequential ways.
*The writer is a nuclear and naval engineer (PhD) and a member of the Brazilian National Academy of Engineering. CEO of Eletronuclear S.A. Coordinator, Brazilian Navy Nuclear Propulsion Program. [IDN-InDepthNews]
Image source: HMAS Stirling
