Vol. VII / No. 15 | October 2026
Authors:
Lavanya Eliana Yudhistira – Undergraduate Student, Department of International Relations, Universitas Indonesia
Summary
AUKUS is a trilateral security partnership between Australia, the United Kingdom, and the United States, established to strengthen power in the Indo-Pacific region. During Pillar I, the ambition was to build nuclear-powered submarines for Australia. However, the long and complex process of developing these submarines created challenges for AUKUS in achieving its goals, especially in creating immediate deterrence to China. China’s growing technological capabilities leading to security threats have led AUKUS to prioritize and accelerate Pillar II. This prioritization aims to develop advanced capabilities faster and create immediate effect against China’s expanding power in the area. Pillar II opens room for external partners, including countries like Japan, whose advanced technological base and geographic position make it a valuable asset. This commentary uses Stephen M. Walt’s Balance of Threat theory to explain why the trilateral security partnership was created and why it prioritized Pillar II. It then examines why Japan, despite its strategic value, remains an external partner rather than a member, arguing that institutional and domestic constraints explain this.
Keywords: AUKUS, Balance of Threat, Pillar I, Pillar II, Japan.
Introduction
As great power competition continues, the dynamics of state security evolve. The growing importance of advanced dual-use technologies has expanded how states assess military and strategic power beyond the quantity of conventional military assets. The growing technological dimension of security threats has transformed the way states approach alliance politics and has grown awareness of the digital sector in national defense. Traditional, rigid military alliances are now being complemented by functional minilateral cooperation focusing on technology development and cybersecurity.
China is seen as having a strong naval power in the Indo-Pacific area, granting them easier access to project power across the Indo-Pacific. The response to threats in the area is clearly illustrated by the formation of AUKUS in 2021, a trilateral security pact between Australia, the United Kingdom, and the United States. As seen on the Pillar I agreement, AUKUS focuses on building Australia’s capacity for nuclear-powered submarines to ensure deterrence against China. AUKUS takes advantage of Australia’s strategic location in the Indo-Pacific. However, the lengthy process of Pillar I has limited AUKUS’s ability to provide immediate deterrence against China.
This condition has led to the implementation of AUKUS Defense Ministerial Joint Statement on 30 May 2026. The ministers of defense from each AUKUS member met to accelerate the implementation of Pillar II (Advanced Capabilities). AUKUS’s acceleration of Pillar II is due to high tech being seen to advance faster and hold more tangible results than the submarine project in Pillar I. AUKUS’s Pillar II shows strategies such as the acceleration of AI technology, quantum technologies, undersea capabilities, and advanced cybersecurity. Pillar II’s focus on advancing technology needed for defense has opened opportunities for external actors, and reflects back AUKUS’ original intention in making Japan a member. Japan’s involvement in AUKUS’ development of military technology projects also raises questions as to why Japan, with great strategic value and who also faces threats from China, is not part of AUKUS by 2026. This commentary first uses the Balance of Threat Theory to explain the formation of AUKUS and its acceleration on the Pillar II. It then explains why Japan, despite its strategic value, has remained an external partner in selected AUKUS projects rather than becoming a member.
The Formation of AUKUS: A Balance of Threat Response to China
According to Stephen M. Walt’s Balance of Threat theory, an alliance is formed to respond to perceived threats and not only to power alone, with threats determined by aggregate power, geographic proximity, offensive capability, and aggressive intentions. The formation of AUKUS is the manifestation of that calculation. The aggregate power is seen through the spike of China’s defense budget as high as 7% and has reached 277 billion USD (Rp. 4,650 trillion). The US Department of War indicates that the number for China’s defense spending is greater, reaching 388-526 billion USD. This isn’t seen merely as statistics, but as a warning of how China’s maritime power is restructuring and becoming a threat to stability around the area.
China’s offensive capability poses a threat through its military advancement. Intercontinental Ballistic Missiles (ICBM) like the DF-61 and DF-31BJ contribute to the broader threat perception among AUKUS members. These capabilities, combined with China’s advancement in Unmanned Undersea Vehicles and Unmanned Aerial Vehicles (UAV), pushes AUKUS to accelerate its own technological development. Even though aggressive intentions are impossible to confirm, militarization in the South China Sea and the constant pressure on Taiwan contribute to the perception of a growing threat. Geographic proximity operates indirectly for AUKUS, since the US is far from China, Australia’s position on the southern edge of the Indo-Pacific gives the US access to sea lanes and straits in Southeast Asia that Chinese military activity could disrupt. Together, these factors lead AUKUS to focus more on deterrence against China.
The Acceleration of Pillar II: Prioritising Dual-use Technology
When it was first formed in September 2021, AUKUS focused primarily on Pillar I, aiming to provide Australia with nuclear-powered attack submarines (SSNs) to deter aggression and preserve stability in the Indo-Pacific. Australia’s commitment is seen through the massive investment of four billion Australian dollarA$ at the start, which can later reach up to thirty billion A$ for the submarine’s infrastructure. However, the implementation of Pillar I is generational and long-term, and it’s estimated to be completed by 2040. The long process limits AUKUS’s ability to respond to China’s rapidly evolving threats. Therefore, AUKUS has prioritized its focus through the acceleration of Pillar II (Advanced Capabilities) as a balancing strategy which offers a faster yet more effective response.
The acceleration of Pillar II reflects the adaptive nature of balancing. AUKUS countries through Pillar II give greater priority to dual-use technologies than to the quantity of military assets. Encompassing eight core areas, including artificial intelligence (AI), cyber capabilities, quantum technologies, undersea capabilities, hypersonics, and electronic warfare, Pillar II serves as a balancing strategy against China while Australia awaits its nuclear-powered submarines. By launching its first Signature Project in mid 2026, the development of AI-driven Unmanned Undersea Vehicles, AUKUS has simplified its technology transfer bureaucracies to generate immediate deterrence, allowing AUKUS to signal to China that its technological integration into military operations has advanced and grown to be an important part of AUKUS’s deterrence strategy.
Japan and AUKUS: Strategic Value versus Domestic and Institutional Constraints
Japan was once seen as one of the strongest candidates to be a part of AUKUS. While Balance of Threat explains AUKUS’s formation, Japan’s absence from membership could be explained by domestic and institutional factors. Since AUKUS’s formation, Washington has signaled interest in integrating Tokyo to strengthen deterrence in the Indo-Pacific. U.S. Ambassador to Japan, Rahm Emanuel (2022-2025), once noted that Japan was projected to become AUKUS’s first partner in Pillar II’s functional projects. Japan’s defense industry, critical geographical position, and advanced technological capabilities are what make Japan a strategic asset in balancing China’s military expansion. The reality says otherwise, the geopolitical urgency of the AUKUS alliance collides with fragile domestic and institutional constraints.
Japan is strategically strong but its institutional framework is not yet compatible with AUKUS. An analysis by Professor Michito Tsuruoka from Keio University in 2024 stated that Japan’s cyber defense architecture and information protection standards have not met the same standard as AUKUS’s members. Japan’s cyber regulations do notdon’t meet information security and anti-espionage standards, especially when Pillar II focuses on highly sensitive military technology sectors such as AI and quantum computing. Even though Japan established a new law back in May 2026 and has launched a new National Intelligence Bureau (NIB), these developments indicate that Japan still has a long way to go before it can be considered to be integrated into the alliance. Japan’s Atomic Energy Law also reflects Japan’s sensitivities around nuclear-related technology. The historical experience of Japan with nuclear weapons also suggests that resistance from the nation might emerge knowing that Pillar I is focused on nuclear-powered submarines. The combination of domestic and institutional limitations explains why Japan stays as an external partner for selected AUKUS rather than becoming a member of AUKUS.
Conclusion and Reflection
AUKUS can be understood as a balancing response to the threat China poses in the Indo-Pacific. Through the Balance of Threat theory, it is seen that the formation is made not only to strengthen power between the three countries, but as a response to China’s spike of rising defense spending, offensive capabilities, technology, and military advancement. AUKUS’s acceleration on Pillar II, focusing more on advanced technological capabilities, shows that balancing is adaptive. AUKUS prioritizes advancing their technology rather than the quantity of conventional military assets seeing the rise of China and how Pillar I will take a long period of time to deliver.
Japan, despite its strategic value, remains an external partner rather than a member of AUKUS. Institutional and domestic reasons such as low standards in regulation, security, and domestic constraints are seen as the reason. Japan’s cyber defense and information protection standards have not reached the same as AUKUS members, which is important since Pillar II involves many uses of sensitive technology. Japan’s law also reflects the possibility that there will be resistance from its people, knowing that AUKUS in Pillar I focuses on nuclear powered submarines. Through Japan, it is proven that a modern alliance doesn’t require a formal format, but can be done through involvement in selected projects, done individually or collectively. Based on the analysis, Japan needs to update their cyber and information security so that they will not lose chances of gaining access to protection and better military technology from other countries, especially AUKUS countries.