Wolves of the sea: Hunter killers and boomers in the Indo-Pacific

While aircraft carriers may serve as some of the most visible and potent symbols of great power force projection and national prestige in the growing arms race between the US and China, submarines are the ultimate predators of the sea.

The highly successful campaigns of terror conducted by the German Navy's 'wolf packs' of submarines during the Second World War to the tactical and strategic brinkmanship between ever more deadly American and Soviet nuclear submarines during the Cold War have set the stage for the 21st century's race for strategic undersea dominance. 

Modern combat submarines are typically broken down by role and either conventional or nuclear propulsion into three different classes, namely: 

• Attack submarines (SSK/SSN): These vessels designed specifically to hunt and kill enemy submarines, surface combatants and merchant vessels. These submarines also serve a protective role, escorting major naval strike groups, logistics and troop convoys and merchant vessels. Recent advances in propulsion, power generation and weapons systems have also enabled these vessels to conduct long-range land strikes using torpedo or vertically-launched cruise missiles. 
• Ballistic missile submarines (SSBN): Significantly larger than their smaller, more nimble hunter killer focused cousins, ballistic missile submarines serve as the sea-borne leg of a traditional nuclear deterrence triangle, armed with submarine launched ballistic missiles capable - these submarines, often termed 'boomers', serve as the ultimate in strategic insurance for great powers like the US and China. 
• Cruise missile submarines (SSG/SSGN): Often modified ballistic missile submarines, cruise missile submarines leverage the unlimited range of nuclear powered vessels combined with advances in weapons technology to pack vast numbers of land attack and anti-ship cruise missiles into specially modified vertical launch systems to provide immense levels of conventional strike capabilities.

For both the US and China, these vessels serve as powerful platforms critical to tactical and strategic planning, forcing both side to consider the availability, location and number of these force multipliers in the Indo-Pacific. 

The heavyweight champion

The US Navy operates a number of different submarines in the Indo-Pacific region, including fast-attack submarines, ballistic missile submarines and cruise missile submarines, which are responsible for providing surface fleet anti-submarine warfare cover, strategic deterrence and long-range strike capabilities.

However, a large portion of the US Navy's submarine fleet is made up of Cold War-era vessels, designed to patrol, hunt and stalk their Soviet counterparts in the north Atlantic, an operating environment vastly different to that of the Indo-Pacific. In response, the US has embarked on a period of rapid modernisation for the submarine fleet, with new Virginia Class attack submarines delivered almost annually and design progress on the next-generation Columbia Class ballistic missile submarines ever closer to beginning construction. 

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America's Indo-Pacific submarine fleet is based at a number of key locations, including Naval Base Pearl Harbor; Naval Base Kitsap, Washington; Naval Base Guam and Naval Base Yokosuka, Japan. 

Never the less, the US maintains a potent force of submarines in and around the region, including a range of attack and ballistic missile submarines: 

Attack submarines (SSN):

• Los Angeles Class: Designed during the height of the Cold War to counter increasingly quiet Soviet submarines in the north Atlantic and north-western Pacific, which would pose a threat to the US Navy's carrier battle groups. The 32 remaining operational vessels weigh in at just under 7,000 tonnes when submerged and are reportedly capable of 33+ knots submerged, the Los Angeles Class are capable carrying 37 Mk 48 heavyweight torpedoes, Tomahawk land attack cruise missiles, Harpoon anti-ship missiles and multiple mines.
• Seawolf Class: The three Seawolf Class subs were designed to be the ultimate predators of the sea, responsible for hunting down stealthy Soviet Akula and Typhoon Class submarines in a deep ocean environment. Seawolf Class subs range in weight from 9,140 tonnes to 12,140 (for the USS Jimmy Carter subclass), capable of 35 knots while submerged and carry approximately 50 Mk 48 heavyweight torpedoes, Tomahawk land attack cruise missiles and Harpoon anti-ship missiles.
• Virginia Class: Acting as the next evolution of US submarine design from the preceding Seawolf Class, Virginia and her projected 66 sister ships are a 21st century submarine, with a classified top speed of greater than 25 knots submerged and submerged weight of 7,900 tonnes. The various 'blocks' of the Virginia Class are capable of carrying a variety of weapons, including Mk 48 heavyweight torpedoes, Tomahawk land attack cruise missiles and Harpoon anti-ship missiles. 

Ballistic missile and cruise missile submarines (SSBN/SSGN):

• Ohio Class: Originally designed as ballistic missile submarines responsible for carrying the sea-based leg of America's nuclear deterrent, the early-to-mid 2000's conversion of four submarines to be classed as cruise missile submarines reduced the total number of ballistic missile submarines to 14. Weighing in at about 18,750 tonnes submerged and a reported submerged speed of 25 knots, the SSBN variants are capable of support 24 Trident I and II missiles, while the SSGN variant carry a payload of 154 Tomahawk land attack cruise missiles, Mk 48 heavyweight torpedoes and Harpoon anti-ship missiles.

The under dog 

China's transition from a brown/green water navy to a fully fledged blue water naval powerhouse has seen the nation rapidly growing its fleet of both nuclear and diesel-electric submarines, which unlike the US are not split between operational requirements in the Atlantic and Mediterranean, enabling China's rapidly developing submarine fleet to focus the entirety of its attention on the Indo-Pacific region. 

This focus has enabled China to deploy a range of advanced nuclear and conventional attack and ballistic missile submarines, including: 

Attack submarines (SSK/SSN:) 

• Type 039/A Class: The first fully Chinese developed conventional submarines, both the Type 039/A Class submarines are designed to supplement the larger nuclear submarines in the anti-shipping and anti-submarine operations in littoral waters. The vessels have a submerged weight of 2,250 tonnes, with a top speed of 22 knots and are capable of carrying 18 533mm torpedoes, the YJ-8 anti-ship cruise missile or 36 naval mines.
• Kilo Class: Russian designed fast attack submarines, designed to key anti-shipping and anti-submarine operations in littoral waters. Larger than the Type 03/A Class vessels, the Russian designed submarines have a submerged weight of 3,000-3,950 tonnes, a submerged speed of 20 knots and submerged range of approximately 740 kilometres. The heavily armed vessels are capable of carrying 533mm torpedoes, 24 mines and, in the case of Russian use, four Kalibr land-attack cruise missiles, eight Strela-3 or Igla-1 surface-to-air missiles.  
• Type 091 Class: China's first generation of nuclear attack submarine weighs in at 5,500 tonnes when submerged, with a top speed of about 25 knots and is capable of carrying 20 533mm torpedoes or 36 mines in their torpedo tubes. Additionally, the vessels are capable of carrying submarine launched variants of the C-801 anti-ship missile.
• Type 093 Class: China's second generation of nuclear attack submarine weighs in at 7,000 tonnes while submerged, with a top speed of 30 knots. The vessels were designed as a replacement for the Type 091 vessels with key improvements on speed, reliability, acoustic performance and capability. The Type 093 carry a variety of weapons, including 533mm torpedoes, submarine launched variants of the CJ-10 missile and YJ-18 anti-ship cruise and land attack cruise missiles.

China's naval modernisation and expansion has also seen significant focus in developing the sea-borne element of its nuclear deterrence triad, with major breakthroughs made in enhancing the stealth, endurance and capability of both the ballistic missile submarines and their ballistic missile delivery systems to maintain Chinese nuclear deterrence. 

Ballistic missile submarines (SSBN):

• Type 092 Class: China's first SSBN design, the single ship is capable of maintaining a max speed of 22 knots. Weighing in at 8,000 tonnes submerged, the vessels also carry 533mm torpedoes and up to 12 JL-1A submarine launched ballistic missiles with an operational range of 2,500 kilometres.
• Type 094 Class: China's second SSBN design, sees an enlarged design of 11,000 tonnes submerged, with a highly-classified speed. The vessels are armed with JL-2 submarine launched ballistic missiles with a range of 7,400 kilometres.

Both China and the US are increasing research and development into developing these potent tactical and strategic platforms, while also focusing on expanding acquisition quotas for the vessels. Submarines play a critical role in the strategy for maritime and even more broadly, multi-domain dominance planning for both nations. 

Nevertheless, the regional submarine race will see approximately half of the world's combat submarines operating in the Indo-Pacific by the mid-2030s, challenging the capabilities of the major powers to effectively use submarines in a congested and contested operating environment. 

In the next part of this series we will take a look at the development and introduction of fifth-generation combat aircraft like the F-35 Joint Strike Fighter and J-20, and Japan's plans to develop its own fifth-generation fighter jet.