In April 2009, Australia announced its "biggest military buildup since World War II" in response to the changing regional security environment, specifically citing declining U.S. supremacy in the Pacific Ocean and China's rapidly growing navy.[1] This public announcement from a long-time, extremely loyal U.S. ally and friend should have been a loud wake-up call for the U.S. Congress, the U.S. Navy, and senior defense officials.

The People's Republic of China (PRC) is rapidly emerging as a regional naval power and a potential global power, which "raises the prospect of intensifying security competition in East Asia both between the United States and China and between China and Japan."[2] Other Pacific countries in the region have also taken note of the changing security environment as evidenced in particular by their planned submarine acquisitions. Australia's military buildup includes doubling its submarine fleet from six submarines to 12 larger, more capable submarines.[3] In addition, "India, Malaysia, Pakistan, Indonesia, Singapore, Bangladesh and South Korea are planning to acquire modern, conventional submarines."[4] Both Australia and India have explicitly described their naval buildups as responses, at least in part, to China's naval buildup.

In contrast, the U.S. submarine fleet is projected to continue shrinking through 2028, further limiting the U.S. ability to shape and influence events in the Pacific. The U.S. attack submarine serves an important part in establishing sea control and supremacy, and it is not interchangeable with other assets. Its unique capabilities make it a force multiplier and allow it to "punch above its weight." To protect U.S. interests in East Asia and the Pacific, and to support and reassure U.S. allies, the U.S. must halt and then reverse the decline of its submarine fleet as a critical component of a broader policy to maintain the military balance in the Pacific.

Underwater Hide and Seek

Combining stealth with powerful weapon systems, submarines are uniquely suited to fulfill a wide range of missions, including strategic deterrence, sea control and denial, battlespace preparation, surveillance and intelligence gathering, special operations landings, and support for ground operations including land attack. Stealth is a primary ingredient to effective submarine operations. It enables a submarine to launch a sudden, devastating strike from an unexpected direction and to slip in and out of an area like a ghost. Stealth is also a submarine's primary defense because a submarine is extremely vulnerable to attack if discovered.

The four main types of submarines--diesel-electric attack submarines (SSs and SSKs), nuclear-powered attack submarines (SSNs), guided-missile submarines (SSGNs), and ballistic missile submarines (SSBNs)--are differentiated by their primary armaments and propulsion systems.

Armament. The primary mission of attack submarines is to achieve sea supremacy by finding and eliminating enemy surface ships and submarines. Most modern attack submarines can also launch cruise missiles, which give them the capability to strike land targets. SSGNs armed with cruise missiles can either conduct sea supremacy missions against surface targets or attack land targets.[5] SSBNs armed with submarine-launched ballistic missiles (SLBMs) serve as part of the U.S., the Russian, and, soon, the Chinese nuclear deterrents.

Propulsion. The type of propulsion largely determines a submarine's capabilities, including range, endurance, speed, agility, and how quietly it can move undetected into and out of harm's way.

Many countries have deployed diesel-electric submarines, which are powered by a diesel engine when running on the surface and by electric batteries when submerged. When submerged, this type of submarine can be extremely quiet. Russia's Kilo-class submarines have earned the nickname "Black Hole" for their ability to evade detection.[6] However, this impressive stealth comes at the cost of limited range and speed and the need to resurface frequently--at least every few days--to recharge batteries.

Several countries have deployed non-nuclear, air-independent propulsion (AIP) submarines (SSPs), which are similar in stealth and speed to traditional diesel-electric submarines, but can remain submerged for weeks at a time.[7] Clearly, this ability to remain submerged for protracted periods makes them less vulnerable to detection.

The major advantage of nuclear-powered submarines is their almost unlimited power reserves, which allow higher operating speeds, virtually unlimitedrange, and the ability to remain submerged for months at a time--limited only by their space to store provisions for the crew and the crew's endurance. Their major disadvantage is that nuclear reactors are inherently noisier than electric motors running on battery power, but this can be mitigated by materials and designs that reduce the submarine's acoustic signature. Nuclear-powered submarines have also become a source of international prestige. Few countries outside the five permanent members of the U.N. Security Council have nuclear submarines.

Anti-Submarine Warfare. Anti-submarine warfare (ASW)is the use of ships, aircraft, submarines, and other platforms to detect, track, and destroy enemy submarines. Submarines are arguably the best ASW platforms because they are designed to operate in the same environment as their targets and have similar strengths and vulnerabilities. However, ASW helicopters and maritime patrol aircraft have advantages in range and speed, and they are almost invulnerable to the submarines they hunt.[8] Surface ships can be tremendously capable ASW platforms, but are more susceptible to submarine attack.

Destroying an enemy submarine--or at least forcing it to retire from the battlespace--first requires detection, usually by sonar. Active sonar-- the pings popularly portrayed in movies of World War II--can give the precise location of a sonar contact (e.g., the submarine), but it also reveals the location (or at least the bearing) of the sonar emitter and warns the enemy submarine that someone is looking for something. Passive sonar relies on "listening" to sonic and ultrasonic waves for the distinctive sounds of a submarine (or other ship). Modern passive sonar systems use computers to filter and interpret the sounds detected by sonar arrays towed by ships, sonar buoys, and other underwater sensors. Ideally, they identify the bearing, location, and type of the sonar contact.

Aircraft or satellites can also detect submarines just below the water surface, and satellites have successfully detected submerged submarines by identifying the effects of their movement through the water on the surface pattern of waves, although this capability is limited by "noise" from other sources, especially in turbulent seas.[9] Modern ASW is a challenging and costly endeavor that requires highly skilled experts, extensive training, and advanced equipment.

Submarine Fleets in the Pacific Ocean

Submarine fleets and deployments have changed dramatically since the end of the Cold War.[10] During the 1990s, Russia withdrew most its submarines from service, and the U.S. steadily drew down its submarine force. While the number of U.S. submarines continues to decline, China is rapidly expanding and upgrading its submarine fleet. In response to a shifting military balance, other countries in the Pacific are also expanding and modernizing their fleets.

United States. The U.S. force of attack submarines fell from 102 boats in 1987 to 53 in 2009.[11] The decline has followed repeated revisions of the Navy's force structure plans since the Reagan-era 600-ship Navy called for 100 SSNs. The 1991 plan of George H. W. Bush called for 80, the Joint Chiefs of Staff (JCS) force-level study of 1992 reduced the goal to 55, and the 1997 Quadrennial Defense Review (QDR) lowered the bar further to 50 SSNs.[12] The 2001 QDR reinstated the goal of maintaining 55 SSNs.[13] The 2006 QDR stated the goals of increasing production to two submarines per year by 2012 and deploying 60 percent of the U.S. submarine fleet to the Pacific to protect U.S. interests in that region.[14] The Navy's current proposal for a 313-ship fleet includes 48 SSNs, although some informed observers have questioned whether this number is sufficient to meet U.S. needs.[15]

The 1999 JCS Submarine Force Structure Study concluded that the optimal number of attack submarines to serve all of the military's and intelligence community's operational and collection requirements would be 68 SSNs in 2015 and 76 in 2025. A force of 55 SSNs in 2015 and 62 in 2025 was deemed a moderate security risk.[16] However, the current fleet of 53 nuclear-powered attack submarines[17] is smaller than even the moderate risk force proposed before September 11, 2001. The fleet is already overstretched, yet under the Navy's long-range procurement plan, the number of SSNs will fall below 48 boats between 2022 and 2033, bottoming out at 41 in 2028 and 2029.[18] (See Chart 1.)

To mitigate the projected "sub gap," the Navy is considering reducing Virginia-class construction time to 60 months, extending the service life of some Los Angeles-class subs by up to two years, and lengthening some deployments from six months to seven months. If successful, all of these measures combined would result in the force bottoming out at 44 or 45 submarines.[19] Yet these stopgap efforts will merely succeed in maintaining a force more appropriate to the pre-9/11 moderate risk scenario.

Neglected ASW Capabilities. The declining SSN force poses a challenge not only to the Navy's ability to maintain effective underwater deterrence, but also to the Navy's ASW efforts, which are already suffering from declining numbers of other ASW platforms.[20] The Navy has 173 aging P-3C patrol aircraft,[21] and the P-8A (the P-3C's replacement) is not scheduled to begin entering service until 2013. The Navy is also retiring the S-3B Viking, its only long-range carrier-based ASW aircraft, and has no plans to replace it.[22]

In addition, "[t]he Navy lacks a modern equivalent of the Sound Surveillance System (SOSUS), the theater-wide acoustic detection system developed in the 1950s to detect Soviet submarines."[23] This is emblematic of broader weaknesses. Many systems deployed during the Cold War are of limited usefulness in today's threat environment. For example, fixed sensors used during the Cold War are not located in areas where conflict is most likely to occur this century. Furthermore, more countries are deploying advanced submarines that could threaten U.S. aircraft carriers, raising the stakes of U.S. military intervention.

Navy force structure must adapt to this evolving underwater threat environment. In July 2008, Navy officials testified before Congress about prioritizing relevant naval combat capability and recent developments that significantly changed how they view current threats. Vice Admiral Barry McCullough described the Navy's new perception of the threat environment:

Rapidly evolving traditional and asymmetric threats continue to pose increasing challenges to Combatant Commanders. State actors and non-state actors who, in the past, have only posed limited threats in the littoral are expanding their reach beyond their own shores with improved capabilities in blue water submarine operations, advanced anti-ship cruise missiles and ballistic missiles. A number of countries who historically have only possessed regional military capabilities are investing in their Navy to extend their reach and influence as they compete in global markets. Our Navy will need to outpace other navies in the blue water ocean environment as they extend their reach. This will require us to continue to improve our blue water anti-submarine and anti-ballistic missile capabilities in order to counter improving anti-access strategies.[24]

The Navy has acknowledged its atrophying ASW capabilities in the face of "a re-emerging undersea threat" and has set the goal of developing more advanced sensors and anti-submarine weapons in the coming years.[25] The U.S. Pacific Fleet has reportedly already increased ASW training.[26] These are critical efforts that must be sustained alongside a goal to increase the procurement of additional ASW platforms--primarily submarines and long-range maritime surveillance aircraft.

China. Since the end of the Cold War, the People's Liberation Army Navy (PLAN) of the People's Republic of China has dramatically expanded and upgraded its navy, especially its submarine fleet, which is "now considered the PLAN's most 'potent strength.'"[27] According to the Pentagon, China has the largest naval force in Asia,[28] including 60 attack submarines (six SSNs and 54 diesel attack submarines).[29] More than half of its diesel submarines are the more modern Kilo-class, Song-class, and Yuan-class submarines.[30] One observer has noted that "China now has more submarines than Russia, and the speed [at which] they are building them is amazing."[31]

Submarine Fleet Expansion. China is well on its way to achieving its goal of building a credible blue-water navy that can project power well beyond its shores:

In order to grasp the energy that China is now committing to undersea warfare, consider that during 2002-2004 China's navy launched thirteen submarines while simultaneously undertaking the purchase of submarines from Russia on an unprecedented scale. Indeed, China commissioned thirty-one new submarines between 1995 and 2005. Given this rapid evolution, appraisals of China's capability to field competent and lethal diesel submarines in the littorals have slowly changed from ridicule to grudging respect of late. China's potential for complex technological development is finally being taken seriously abroad.[32]

Estimates of the future size of China's attack submarine fleet vary widely from 58 boats to 88 boats,[33] depending on how quickly older submarines are retired from service, whether building more expensive SSNs will reduce total submarine production, and additional purchases of foreign-built submarines. In recent years, China has introduced four new classes of domestically designed and built submarines: Jin or Type 094 (SSBN), Shang or Type 093 (SSN), Yuan or Type 041/039A (SSP), and Song or Type 039/039G (SSK). A successor to the Shang-class is reportedly in development.[34] This degree of sustained investment in submarine development and building suggests that the upper end of the range (possibly 70 or more) is a more realistic estimate of PLAN force structure in the coming decades.

Increased Patrols. The Chinese attack submarine fleet has noticeably increased its patrol rate from two patrols in 2006 to six in 2007 to 12 in 2008.[35] This suggests a new focus on training and a desire to demonstrate to other actors, particularly the United States, that China is a maritime power in the Pacific. Two recent incidents highlight this trend. On October 26, 2006, a Chinese Song-class submarine surfaced within five miles of the aircraft carrier USS Kitty Hawk--inside its screen of escorts--which was operating near Okinawa.[36] On June 11, 2009, a Chinese submarine collided with the USS John S. McCain's towed sonar array off the Philippines.[37] Whatever these incidents may or may not reveal about the limitations of U.S. ASW capabilities and the competence of Chinese submariners[38]--the most useful information is almost certainly classified--they clearly demonstrate that China's submarines are ranging farther afield and operating more aggressively than in the past.

Objectives.A number of considerations and objectives could help to explain China's rapid expansion of its attack submarine fleet: basic Chinese defense needs, limiting the U.S. ability to "interfere" in China-Taiwan relations, challenging U.S. dominance in the Pacific, protecting the Chinese SSBN nuclear deterrent, and winning greater international prestige.

First, the bulk of China's wealth and population is concentrated on its east coast, which gives China a compelling reason to deploy a robust naval deterrent along that coast.

Alternatively, many security experts argue that "China's main objective in upgrading its submarine fleet is the ability to delay or deter a United States intervention on behalf of Taiwan."[39] China has been bedeviled by the "renegade province" of Taiwan and by U.S. meddling (from China's perspective) in cross-strait relations since 1949. When relations across the Taiwan Strait became particularly tense in 1996, the U.S. sent two carrier battle groups to the area to deter Chinese aggression against Taiwan. Unsurprisingly, China has since placed a high priority on developing sea denial capabilities that could discourage and, if necessary, delay or prevent U.S. military intervention in a future cross-strait dispute.[40] The U.S. Department of Defense has concluded that, "Acquisition and development of the Kilo, Song, Shang, and Yuan-class submarines illustrates the importance the PLA places on undersea warfare for sea denial."[41]

The PLAN may also be emulating Soviet naval strategy, which "rapidly overcame the [Soviet Union's] unfavorable geostrategic situation" by using nuclear submarines to give it "an ocean-going navy with offensive capability."[42] A similar strategy would help the PLAN to break the "island chain blockade" of mainland China. The new naval base on Hainan Island adds an additional wrinkle, giving the PLAN "direct access to vital international sea lanes, and offer[ing] the potential for stealthy deployment of submarines into the deep waters of the South China Sea."[43]

As part of its nuclear deterrent, China is expected to build as many as five Jin-class SSBN submarines, each armed with 12 SLBMs capable of reaching U.S. territory from positions off the Chinese coast. This would constitute a credible sea-based nuclear deterrent.[44] China may want to use some of its SSNs to escort SSBN deterrence patrols.[45]

Finally, it seems clear that China intends to become a global power, and "it appears to be conventional wisdom in the PRC that nuclear submarines represent one of China's clearest claims to status as a great power."[46] A strong attack submarine fleet would also help to protect Chinese shipping around the world. The Yin He incident in 1993 helped to solidify this concern among PRC leaders, who were "extremely furious, but had no recourse" when the U.S. insisted on inspecting a Chinese freighter suspected of carrying ingredients of chemical weapons to Iran.[47]

Australia. Australia has six diesel-electric submarines and has announced plans to replace them as part of a broader naval modernization program with 12 modern conventional submarines armed with cruise missiles.[48] The Australian government has explicitly tied this expansion to the rise of China as a naval power and weakening U.S. naval supremacy,[49] which Australia believes has "played a stabilizing role across the world and especially so in the Asia-Pacific region."[50]

India. While geographically not a Pacific country, India exercises growing influence in Southeast Asia and the western Pacific. India has 16 diesel-powered attack submarines and recently launched its first SSN, which is based on the Russian Akula-class. India will lease a second Akula-class submarine from Russia and is building six Scorpene-class diesel submarines.[51]

India's planned expansion and upgrade of its submarine fleet is part of a larger effort to add more than 100 warships to the Indian navy over 10 years. The Indian Ministry of Defense explains the shipbuilding program as a "strategic necessity" of national defense, largely in terms of countering the Chinese naval buildup: "China is developing its navy at a great rate. Its ambitions in the Indian Ocean are quite clear."[52] India also aspires to become a great power, and submarines are seen as an integral part of any major power's fleet.

Russia. The Russian (formerly Soviet) submarine fleet shrank by almost two-thirds after the collapse of the Soviet Union. In recent years, the Russian navy has emerged from its post-Soviet crisis, but still needs to decommission dozens of nuclear submarines left over from the Cold War. In 2009, Russia had 17 SSNs and 20 diesel submarines, of which five SSNs and nine diesel submarines were assigned to the Pacific fleet.[53] Despite massive budget increases in recent years, "the navy is haunted by insufficient funding, which limits its ability to conduct regular overhauls of operational submarines and even to maintain them in a combat-ready state."[54]

Japan. Japan maintains a modern submarine fleet of at least 16 boats, including at least one new Soryu-class AIP submarine.[55] Japan has historically replaced its submarines after about 16 years of service, much more quickly than other countries retire theirs.[56]

South Korea. South Korea has 12 attack submarines and plans to increase its fleet to 27 by 2020.[57]

North Korea. North Korea has 22 old conventional attack submarines (how many are serviceable is unknown) and numerous mini-submarines.[58] While its submarines could theoretically threaten merchant shipping and unsophisticated naval combatants,[59] North Korea's submarines are not viewed as serious contenders in sea control operations.

Taiwan. Taiwan operates two attack submarines and has explored numerous options to expand and upgrade its submarine fleet, including domestic construction. In 2001, the U.S. offered Taiwan an arms package that included eight diesel-electric submarines, but the U.S. does not own the rights to any current diesel submarine designs, and the proposal appears to be dead.[60]

Southeast Asia. In the context of China and India deploying nuclear-powered submarines, most countries in Southeast Asia are expanding or upgrading their existing submarine fleets. Indonesia has two submarines and has announced a plan to build 12 submarines by 2024.[61] Vietnam has ordered six Kilo-class submarines from Russia.[62] Singapore has recently acquired two Archer-class AIP submarines to replace two of its four aging boats.[63] In October 2007, Malaysia received delivery of its first submarine, a Scorpene-class boat built in France. The second is scheduled for delivery in 2010.[64] Thailand has no submarines, but has expressed increasing interest in acquiring several.[65]

Sustaining U.S. Undersea Supremacy

Over the past 16 years, China has rapidly expanded its submarine fleet while the U.S. has steadily drawn down its submarine forces even as combatant commanders have demanded more of their capabilities. U.S. allies and friends have expressed legitimate concerns about the shifting security environment in the Pacific.

The U.S. has acknowledged this shifting balance--at least in part--and has begun to address it. The Navy appears to be on course to fulfilling the 2006 Quadrennial Defense Review directive to deploy 60 percent of the U.S. submarine fleet in the Pacific,[66] but deploying a higher percentage of a shrinking fleet will likely prove less effective than increasing the total number of submarines.

To halt and eventually reverse the erosion of U.S. undersea supremacy in the Pacific Ocean, to reassure and support U.S. allies, and to protect long-standing U.S. interests in the region, the U.S. should:

• Build additional attack submarines more rapidly. Congress should increase procurement of Virginia-class submarines to at least two per year with the objective of fielding a force of at least 60 fast attack submarines.[67] Yet by itself, procuring new boats at the rate of two per year will not replace the Los Angeles-class submarines as quickly as they are scheduled to be decommissioned.
• Overhaul and modernize selected Los Angeles-class submarines to extend their service life. While overhauling and modernizing submarines will require additional funding, extending the service life of older submarines that are still in good condition--instead of decommissioning them as planned--would help to close the "sub gap" over the short term at a lower cost than drastically increasing submarine construction.
• Forward-base more submarines. Basing more submarines in Guam, Hawaii, and possibly Japan--in addition to the three SSNs already based in Guam--would place them closer to East Asia, where their services are most likely to be needed, and would allow them to maximize time on station and minimize travel time to and from their home ports.[68] The Navy should also consider acquiring additional submarine tenders, which would allow the creation of temporary forward bases where submarines could rotate crews and rearm.
• Reevaluate the use of diesel submarines. Congress should direct the Navy to study the utility of using AIP attack submarines to help to close the gap between regional commander requirements and the number of available U.S. submarines. In the short term, as domestic production capabilities develop, the U.S. could buy submarines from U.S. allies.[69] Developing a U.S. conventional submarine capability would also facilitate more robust ASW training and afford the U.S. the option to sell advanced diesel submarines to Taiwan.
• Research, develop, and deploy undersea force multipliers. Fielding unmanned undersea vehicles (UUVs) can enhance the range, capabilities, and lethality of existing undersea weapons, platforms, and sensors.[70] However, UUVs should not be viewed as replacements for attack submarines. The U.S. will need to continue deploying manned submarines for the foreseeable future while upgrading and enhancing their capabilities to counter developing and potential threats.
• Enhance anti-submarine warfare capabilities. Atrophied U.S. ASW capabilities are particularly worrisome because developing skilled ASW personnel requires years of intensive training. Congress should allocate sufficient and stable funding to increase ASW capabilities both qualitatively and quantitatively. Specifically, Congress should increase the number of ASW platforms by expanding and accelerating the P-8 program and by building more ships with ASW capabilities, including more DDG-1000 destroyers or upgraded DDG-51s with towed sonar arrays.[71]
• Work with the militaries of U.S. allies and friends to improve their submarine and ASW capabilities. These efforts should include more frequent and intensive multilateral exercises and maneuvers, technology sharing, and joint planning. Strengthening the capacity and capabilities of friendly foreign navies would allow the U.S. to employ fewer of its own resources in certain contingencies and missions, thereby freeing up U.S. submarines for other pressing needs.
• Encourage greater Chinese transparency in security matters through military-to-military channels. Greater Chinese transparency about its military may resolve or ease some of the concerns about China's naval buildup. Greater understanding may also help to prevent or defuse future incidents involving the U.S. and Chinese militaries. China's failure to give prior notice to the U.S. military of its recent missile defense test--contrary to common international practice--weakens transparency efforts and leads to many unanswered questions.

Conclusion

The shifting security environment in the Pacific Ocean and East Asia has caused serious concern among U.S. allies and friends. Several have responded by launching aggressive naval buildups, and Australia has openly tied its defense buildup to the shifting China-U.S. balance in the Pacific.

The U.S. Navy is still the most powerful navy in the world, and it has the best-trained and most capable submarine force, but its declining numbers have been stretched thin by the demands of ongoing operations and other assigned missions. The continuing decline of the U.S. submarine fleet, in particular, threatens U.S. undersea supremacy in the Pacific and therefore could seriously undermine the Navy's ability to operate effectively in East Asia and the Pacific.

Unless the U.S. rebuilds its submarine fleet and enhances the Navy's ASW capabilities, U.S. military superiority in the Pacific will continue to wane, leading to avoidable political and economic hazards for the U.S. and its friends and allies.

Mackenzie Eaglen is Research Fellow for National Security in the Douglas and Sarah Allison Center for Foreign Policy Studies, a division of the Kathryn and Shelby Cullom Davis Institute for International Studies, at The Heritage Foundation. Jon Rodeback is Research Editor at The Heritage Foundation. Julia I. Bertelsmann, a Research Assistant in the Allison Center, assisted in researching and writing this paper.