The hottest topic in Australia’s defence community right now is how to develop the Royal Australian Navy’s submarine capability. The decision ^[1] to acquire nuclear-powered submarines (SSNs) under the AUKUS partnership and cancel the acquisition of the Attack-class diesel–electric submarines (SSKs) from France’s Naval Group has transformed the Australian discussion about undersea warfare.

The very distant timeline for acquiring the first SSN—be it a US Virginia-class or UK Astute-class boat—has opened up a serious gap in Australia’s undersea warfare capability. Reliance on a life-of-type extension for the RAN’s six Collins-class submarines doesn’t really close that gap. As ASPI’s Marcus Hellyer notes in his latest Cost of Defence report ^[2], there’s a serious risk to naval capability:

In an era of increasing strategic tension, we face the risk of the Collins-class submarine and Anzac class-frigate ceasing to be relevant capabilities before their replacement arrives … [I]t will be the second half of the 2030s before we have useful numbers of Hunter-class frigates and potentially the mid-2040s before we have an SSN capability (as opposed to an initial boat). By that time, the Collins boats will be well into their 40s.

He goes on to suggest three potential solutions to the submarine capability gap. One option is to accelerate the acquisition of SSNs, though that remains an unlikely prospect given the complex web of factors beyond acquiring the boats themselves. Buying an off-the-shelf interim sub that’s smaller and better placed for operating in Australian maritime approaches, including the archipelago to our north, is a second option, and a ‘son of Collins’ SSK based on Saab’s A26 design would be a third.

Our choice among these options must consider why we’re acquiring submarines and what we want them to do. That in turn requires consideration of a broader approach of developing a comprehensive undersea warfare system that comprises not just crewed submarines, but a complete family of capabilities, both surface and subsurface, and even extending into the air and space domains.

The utility of submarines is best defined by the role they excel at, which is hunting and sinking other submarines. But doing that is set to become considerably more challenging, and our acquisition of a small number of submarines—nuclear or conventional—may be insufficient to the task. The rapid expansion of China’s submarine fleet shows no sign of slowing down. The US Office of Naval Intelligence has projected that ‘China’s submarine force will grow from a total of 66 boats … to 76 boats … in 2030’. Among them will be ever quieter and more sophisticated SSNs, such as the Type 093B ^[3] and the future Type 09V ^[4] Sui class, as well as advanced uncrewed underwater vehicles ^[5] (UUVs).

It’s reasonable to expect continued growth of the People’s Liberation Army Navy’s capability through the 2030s. Australia’s six ageing Collins-class boats—even with upgrades—would be no match for a much larger and more capable undersea warfare fleet through to the mid-2040s when the SSNs come online as an operational capability. The imbalance becomes less pronounced given that Australia’s submarine capability is most likely to operate as part of a coalition that could include the US, Japan and potentially the UK. So, it’s not likely to be six Australian boats alone against the might of the PLA Navy. But even with coalition partners, the future undersea battlespace looks decidedly hostile.

Add to this the prospect that China looks set to acquire forward basing arrangements, including potentially in Solomon Islands and at the emerging base in Ream, Cambodia. Forward bases would open up the possibility of PLA Navy SSKs and UUVs ^[6] operating more frequently in Australia’s maritime approaches, in greater numbers, while its advanced SSNs operated from mainland bases to defend China’s maritime approaches in key focal areas such as the South China Sea and around Taiwan, as well as through the first island chain into the middle seas between China and Guam.

China is rapidly closing qualitative capability gaps in anti-submarine warfare (ASW) with its investment in underwater acoustic arrays ^[7] and more advanced ASW corvettes such as the Type 056A Jiangdao class ^[8]. More advanced undersea warfare detection technologies are likely to emerge, particularly as applications of quantum technologies and artificial intelligence are developed, and LiDAR sensors based on satellites will make the oceans far less opaque ^[9] by the 2050s. It will become more difficult to deploy submarines close to China undetected.

With this emerging threat environment in mind, Australia needs to be far more ambitious in its approach to undersea warfare. It’s not just about acquiring a small number of SSNs, or even an interim conventional submarine capability. There needs to be much greater focus on accelerating investment in acquiring sophisticated autonomous underwater and surface vessels in significant numbers to complement crewed platforms on and below the waves.

The RAN’s strategy ^[10] to 2040 for remote autonomous systems and AI doesn’t consider offensive ASW roles for UUVs but instead uses them to track submarines in concert with crewed submarines. This is a missed opportunity because it still relies on limited numbers of crewed platform as shooters with the UUVs as sensors. This ignores the potential benefit that comes from quantity having a quality of its own, and it might be wise to consider whether the acquisition of significant numbers of Australian UUVs in the 2030s could allow them to act as ASW shooters as well.

Greater investment in more capable undersea warfare surveillance systems, including the application of quantum technologies, AI and space-based LiDAR capabilities, could enhance our ability to monitor the undersea domain in our maritime approaches. Some years back I wrote ^[11] about the need to develop theatre ASW based on integrated undersea surveillance systems, and to enhance ^[12] the Australian Defence Force’s maritime patrol and response capability. The 2021 AUKUS agreement mentions ^[13] ‘additional undersea capabilities’ with an emphasis on UUVs. But exploiting advanced hydrophone sensors on the seabed and making full use of large numbers of autonomous surface vessels such as Ocius Technology’s Bluebottle ^[14] would enhance our ability to understand the battlespace, alongside next-generation capabilities such as LiDAR and additional maritime patrol and response aircraft.

The debate over submarines needs to shift from one about platforms, numbers and timelines to a discussion about how Australia and its partners can develop a resilient system-of-systems approach to undersea warfare. Such an approach would tie together multiple sensors on different platforms with both crewed and autonomous systems as shooters while exploiting combat mass. This is vital if we are to effectively operate in an undersea domain that is likely to become much more complex and challenging.