China’s undersea capability: Meeting the challenge

The People’s Liberation Army Navy (PLAN) has been undergoing an intensive modernisation programme for almost three decades, transforming Chinese surface and submarine capabilities. Not only has the PLAN surpassed, sometime in the last decade, the United States (US) Navy in terms of total warships, but Chinese vessels are now more capable than their predecessors and have become comparable to those of the most advanced navies – causing widespread alarm among naval planners in free and open countries. 

This article, the second of a series on underwater warfare, explores how the People’s Republic of China (PRC) is evolving as an underwater power. Specifically, it will identify how the PLAN’s submarine capabilities will affect the strategic environment in the Indo-Pacific and how British interests might be challenged as the PLAN becomes more able to assert itself regionally and beyond.

Submarine numbers and capabilities

The majority of the PLAN’s current submarines are diesel/electric-powered attack submarines, with smaller numbers of nuclear-powered attack submarines (SSNs) and nuclear-powered ballistic missile submarines (SSBNs), comprising a total of around 70 vessels. Unlike its counterparts in the free world, the PLAN does not release shipbuilding plans or details of its strategic goals, so projections and estimations are necessary. These assessments differ slightly on the exact numbers but generally agree that the PLAN’s focus will be on expanding the quantity of the latter two types of boat. Given the one-dimensional nature of the data and the lack of regard to how those vessels are and can be used, raw vessel numbers are a narrow method of assessing naval capabilities, but quantitative trends can be helpful in identifying a navy’s direction of travel in terms of force structure. 

Qualitatively, the PLAN is now building submarines to relatively modern blueprints, sourced domestically and from Russia, which are a significant improvement on the noisy and antiquated designs of its earlier subsurface fleet – PLAN submarines are now far quieter and better-armed and should not be underestimated. From reliance on Russian Kilo class boats purchased in the 1990s, the PRC now produces its own: the Song class and Yuan class diesel/electric-powered attack submarines, the Shang I and II classes of SSN, and the Jin class SSBN. Strategic patrols in the South China Sea by Jin class boats mark the first time that the PRC has put to sea a credible sea-based nuclear deterrent. A new variant of the Shang class is also reported to be forthcoming which can carry land-attack cruise missiles and older variants may be retrofitted to enable such armament as well – adding land-attack capabilities to the PLAN’s submarine fleet, in effect providing the PRC with additional long-range strike options.

The modernisation of the PLAN, including that of the submarine fleet, is centred around the PRC’s desire to achieve and maintain maritime superiority in its immediate periphery, including defending maritime communication lines. This builds on the PLAN’s wider strategy of ‘active defence’ and bolsters its ability to deter outside intervention in any potential conflict over Taiwan. While the PRC is aiming to strengthen its joint force to project power further into the Indo-Pacific and ultimately globally, at present its capabilities (particularly around anti-access/area denial) remain firmly regional and are most robust within the so-called ‘First Island Chain’ (see Map 1).

Map 1: The First and Second island chains

The PLAN’s submarine programme: Geostrategic implications

Mirroring the Integrated Review Refresh, much of the PRC-related security discussion in the United Kingdom (UK) focuses on how His Majesty’s (HM) Government can work with the PRC (both bilaterally and in international forums) on global issues like climate change while also tackling the ‘epoch-defining systemic challenge’ the PRC poses to the open international order. Britain’s priorities will and should remain focused on the Euro-Atlantic theatre, and HM Government seeks to align European NATO allies to keep the growing threat from Russia at bay so the US has more leeway to deter the PRC, particularly if tensions escalate in the Indo-Pacific. However, given the connectivity between the two theatres and the growing economic importance of the Indo-Pacific, it would be myopic, with risks for national security, for Britain to ignore the geopolitics of the region. 

As the PLAN’s capabilities directly bear upon the PRC’s ability to project power in its immediate periphery, the modernisation and expansion of submarine capabilities have the most immediate salience to Taiwan’s security. The Integrated Review Refresh notes the PRC’s ‘more aggressive stance in the South China Sea and the Taiwan Strait’ and reinforces HM Government’s longstanding position on Taiwan that there should not be any ‘unilateral attempts to change the status quo.’ The strategy’s language around greater cooperation and alignment with allies and partners reflects the implicit reality that the UK will only have strategic impact if it acts to empower them should tensions over Taiwan escalate into conflict.

The PLAN’s submarine modernisation efforts underscore the vital importance of British support for allied and partner navies in the Indo-Pacific, building on recent exercises, engagement, and freedom of navigation efforts such as the Carrier Strike Group’s voyage through the region in 2021. The AUKUS agreement is an excellent example of the UK’s determination to exploit its technological expertise for geopolitical gain. In addition to the forward-rotation of a Royal Navy Astute class boat in Australia, the UK is partnering with the US in sharing advanced submarine technology with Australia. It is also working directly with the Royal Australian Navy to develop and build a new class of SSN. The modernisation and expansion of Australian submarine capabilities is an important hedge against increasingly sophisticated and numerous Chinese vessels. Indeed, the new AUKUS class SSNs, as well as the Virginia class boats being purchased in the interim from the US Navy, mean that Australia will be able to build upon its valued contribution to allied presence and deterrence in the Indo-Pacific, enabling the UK to focus more on the Euro-Atlantic. 

The PLAN’s submarine modernisation efforts underscore the vital importance of British support for allied and partner navies in the Indo-Pacific, building on recent exercises, engagement, and freedom of navigation efforts such as the Carrier Strike Group’s voyage through the region in 2021.

The PRC’s naval modernisation and expansion should give HM Government increased incentive to update and grow the Royal Navy’s capabilities. As a maritime power with a strong and technologically advanced defence-industrial base, the UK should focus on expanding shipbuilding capacity and bringing forward the acquisition and manufacture of new ship designs. This is recognised in the National Shipbuilding Strategy with increased investment in the surface fleet, particularly in the Type 26 and Type 31 frigate programmes, and in the upgrading of the UK’s continuous at-sea nuclear deterrent with the ongoing replacement of the Vanguard class SSBNs with the new Dreadnought class. The British submarine fleet will also greatly benefit from the AUKUS agreement, with the new AUKUS class SSNs entering British service in the 2030s – both updating capabilities from the current Astute class boats and potentially expanding submarine numbers, potentially up to 12 SSNs. The upcoming refresh of the Defence Command Paper will offer further opportunities for the UK to grapple with this core issue.

Conclusion: Looking ahead

The PRC’s actions are leading British allies and partners in the Indo-Pacific to develop countermeasures, such as Japan’s military modernisation programme and Australia’s pursuit of an SSN capability. Increasingly hemmed in and pinned down, the PLAN is unlikely to threaten Britain in the European neighbourhood for at least a decade, although British defence planners should keep a weather eye on the PRC’s ambitions in the Arctic and the Wider North. In the shorter term, British support for allies and partners in the Indo-Pacific will be vital in helping to deter Chinese escalation over Taiwan. As the People’s Liberation Army (PLA), including the PLAN, continues to modernise, this deterrence will only become more important. The UK’s focus will rightly continue to be centred on the Euro-Atlantic, but HM Government and the Royal Navy can and should help to undergird the open international order in the Indo-Pacific as well – even without a significant physical presence in the Indo-Pacific, UK security still relies on the free flow of trade, economic stability, and maritime connections in the region, all of which are put under threat by PRC aggression. A modernised PLAN should be met with a swath of new allied naval capabilities, and Britain’s undersea technological and naval expertise means that it can help to make this a reality.

Emma Salisbury is the Robert Whitehead Associate Fellow in Military Innovation. Undertaking a PhD at Birkbeck College, University of London, she is also a senior staffer for a Member of Parliament and an Assistant Editor at War on the Rocks.