Foreign Relations & International Law

Water Wars: AUKUS Goes Hypersonic

Teresa Chen, Alana Nance, Han-ah Sumner
Friday, April 22, 2022, 8:01 AM

Biden administration delivers 2022 National Defense Strategy; China conducts militarization and secret diplomacy in the South China Sea; AUKUS announces new agreement to develop hypersonic weapons; U.S. and Philippine armed forces revive full-scale Joint Exercise Balikatan following coronavirus pause; and more.

U.S. Marines with Marine Heavy Helicopter Squadron 466 (HMH-466) and Marine Light Attack Helicopter Squadron 369 (HMLA-369) execute flight operations on the USS Miguel Keith (ESB-5) ahead of Balikatan 22. Source: U.S. Marine Corps

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2022 National Defense Strategy

On March 28, the Biden administration delivered the classified version of the 2022 National Defense Strategy (NDS) to Congress. The strategy, accompanied by a $773 billion budget proposal, outlines the administration’s vision of how the Pentagon will advance and safeguard U.S. national interests. A Defense Department fact sheet accompanying the strategy outlines four strategic priorities, including pacing defense capabilities to the “growing multi-domain threat” posed by China, deterring “strategic attacks” against the U.S. and its allies, deterring aggression from China and Russia, and building a resilient “Joint Force” and defense ecosystem.

The fact sheet makes clear that China is the Defense Department’s dominant nation-state focus, noting that the U.S. will act “urgently” to strengthen deterrence against China, its “most consequential strategic competitor.” It notes that the U.S. will prioritize the Chinese challenge in the Indo-Pacific over collaboration with NATO allies to face Russia’s challenge in Eastern Europe. The Pentagon’s continued focus on China reflects a continuation of the Trump administration’s 2018 National Defense Strategy 

The strategy appears, in large part, as another step in the Pentagon’s ongoing response to China’s military modernization effort, including its naval modernization. A recent Congressional Research Service report noted that China’s navy poses a novel challenge to the U.S.’s ability to maintain wartime control of “blue-water” ocean areas in the Western Pacific. Observers believe China aspires to act as an anti-access/area-denial force to deter U.S. intervention should a conflict arise over Taiwan. 

Mirroring Biden’s 2022 Indo-Pacific Strategy, the Defense Strategy emphasizes “integrated deterrence” as a cornerstone of its approach to deter aggression and strategic attacks at land and sea. The NDS also reflects the Biden administration’s ongoing efforts to strengthen partnerships with India, Australia, Japan and nations in Southeast Asia to counterbalance China’s influence in the Indo-Pacific region. Mara Karlin, assistant secretary of defense for strategy, plans, and capabilities, echoed this priority recently, noting that “security cooperation” is an ongoing area of growth for the Defense Department. 

The strategy also emphasizes the need to “build enduring advantages” for the Joint Force through technological advances and accelerated force development. The defense budget saw a $10 billion increase over the enacted fiscal year 2022 budget, aimed at achieving these ends by “modernizing the force” and “making it more capable to compete with near-peer adversaries.” The Pentagon has asked for $6.1 billion to fund U.S. military activities in the Pacific. It has also described plans to decrease the number of active-duty troops in the Army, Marines and Navy and to increase numbers for the Air Force and Space Force. The Navy hopes to retire 24 ships while building nine new surface ships and submarines but has faced significant pushback from navalists such as Rep. Elaine Luria, a former Navy officer and frequent critic of the Navy’s strategic priorities. The budget also called for $34.4 billion for nuclear modernization to help fund a Columbia-class ballistic missile submarine and a Ground Based Strategic Deterrent missile. 

Security Developments in the South China Sea

Chinese Militarization

The Chinese military has increased night drills and is exercising its newly upgraded fighter jets in the South China Sea. The exercises have included underwater reconnaissance, surface-to-surface strikes, air-defense, amphibious landings, air-to-air combat drills and cross-regional flights aimed at testing pilots’ stamina. A researcher from the Beijing-based Yuan Wang military science and technology think tank said that the series of drills represents a “countermeasure” in response to the activities of U.S. warships and aircraft within the South China Sea; namely, freedom of navigation operations (FONOPS). China is simultaneously expanding its nuclear arsenal and undertaking construction on more than 100 suspected missile silos in order to modernize its nuclear deterrent capability.

China also appears to have completed militarization of three artificial islands within the hotly contested Spratly Island chain (Chinese: Nánshā Qúndǎo; Filipino: Kalayaan Islands; Vietnamese: Quần đảo Trường Sa), according to U.S. Indo-Pacific Commander Adm. John Aquilino. The three islands, known as Mischief Reef (Chinese: Měijì Jiāo; Filipino: Panganiban Reef; Vietnamese: Đá Vành Khăn), Subi Reef (Chinese: Zhǔbì Jiāo; Filipino: Zamora Reef; Vietnamese: Đá Su Bi), and Fiery Cross Reef (Chinese: Yǒngshǔ Jiāo; Filipino: Kagitingan Reef; Vietnamese: Đá Chữ Thập), were once low-tide elevations (LTEs), defined by UNCLOS Article 13 as naturally formed areas of land that are surrounded by and above water at low tide but submerged at high tide. As features of the Philippines’ continental shelf, the LTEs are subject to the Philippines’ exclusive jurisdiction and right to authorize construction of artificial islands under UNCLOS Articles 60 and 80. China began land reclamation efforts in the Spratly Islands LTEs in December 2013 without seeking authorization from the Philippines, and in 2016 an international tribunal ruled that China’s actions were in violation of international law. 

In what is known as the South China Sea Arbitration, the tribunal effectively rejected China’s “nine-dash line” historic rights claim over much of the South China Sea. China refused to accept the tribunal’s ruling and continues to assert its sovereignty over the artificial islands it has constructed on the Philippines’ continental shelf. In 2015, Chinese President Xi Jinping assured the U.S. that the islands under construction would not be militarized. Over the past month, however, China has defended its buildup of anti-ship and anti-aircraft missile systems, jamming equipment, and fighter jets on the islands, claiming that they are “necessary national defense facilities.” Vice President Kamala Harris criticized Beijing for undermining the rules-based order and threatening the sovereignty of other South China Sea nations. Although (under UNCLOS Articles 60 and 80) artificial islands do not possess the legal status of natural islands and do not affect the delimitation of a state’s territorial sea, exclusive economic zone (EEZ), or continental shelf, the islands are still significant. Strategically located within major maritime navigation routes, the islands allow China to project military power further throughout the region in the manner of the so-called unsinkable aircraft carriers of the World War II Pacific theater. Adm. Aquilino asserted that the three islands function to “expand the offensive capability of the [People’s Republic of China] beyond their continental shores.”

In a similar vein, a document leaked on Twitter at the end of March revealed that China and the Solomon Islands may be on the verge of signing a security agreement that would allow the Solomon Islands to call upon the Chinese government to provide military and law enforcement personnel to maintain “social order” in exchange for China’s ability to use the archipelagic state for “logistical replenishment,” “stopover” and “transition.” The leaked agreement caused concern among the U.S. and regional allies that it would lead to establishment of a Chinese base in the Solomon Islands, a strategically located archipelago just northeast of Australia. New Zealand Prime Minister Jacinda Ardern described such acts as “potential militarization of the region.” Solomon Islands Prime Minister Manasseh Sogavare denounced these concerns as “insulting” and criticized foreign powers for “assuming that the Solomon Islands could not act in its own best interests.” Chinese Foreign Ministry spokesman Wang Wenbin also called for other countries to “earnestly respect Solomon Islands’ sovereignty and its independent decisions instead of deciding what others should and should not do self-importantly and condescendingly from a privileged position.” As of April 1, Sogavare maintains that concerns about development of a Chinese base in the Solomon Islands are “misinformation” and that the agreement does not invite China to establish a base.

AUKUS Announced a New Agreement to Develop Hypersonic Weapons

Australia, the U.K. and the U.S. announced on April 5 that they will work together via the recently created security alliance AUKUS to develop hypersonic and counter-hypersonic capabilities. The military agreement is a new element of the AUKUS alliance, originally created in September 2021 to help Australia develop nuclear-propelled submarines. In a joint statement, the leaders of AUKUS—Prime Minister Scott Morrison of Australia, Prime Minister Boris Johnson of the United Kingdom, and President Joe Biden—stated that they were committing “to commence new trilateral cooperation on hypersonics and counter-hypersonics, and electronic warfare capabilities, as well as to expand information sharing and to deepen cooperation on defense innovation.”

Hypersonic missiles—which can carry nuclear or conventional warheads—fly at speeds of at least Mach 5 (five times the speed of sound), faster than conventional cruise missiles. Because of their speed, maneuverability, and low altitude of flight, hypersonic weapons could challenge conventional detection and defense systems, limiting the amount of time decision-makers have to assess their response options and to intercept the attack. U.S. defense officials in recent years have stated that both terrestrial- and current space-based sensor architectures are insufficient to detect and track such weapons.

The AUKUS agreement comes as the U.S. and its allies grow concerned about China’s military assertiveness in the Indo-Pacific region, and after Russia used hypersonic missiles in airstrikes last month during its invasion of Ukraine. It also comes as the U.S. has shown a growing interest in pursuing the development and near-term deployment of hypersonic systems, which may be motivated, in part, by advances in these technologies in Russia and China. China, for example, conducted a test of a hypersonic weapon system last year, which the U.S. confirmed in October 2021. Days after Russia’s use of hypersonic missiles in Ukraine, the U.S. quietly conducted its own test, and announced its success weeks later in early April. Although the U.S. has been developing hypersonic missiles as part of its conventional prompt global strike program since the early 2000s, hypersonic missiles have become an increased defense focus. The Pentagon’s 2023 budget request includes $4.7 billion for research and development of hypersonic weapons, reflecting a “huge jump in the budget” from previous years, according to defense officials. During a House Armed Services Committee hearing on April 5, Defense Secretary Lloyd Austin stated that he has been engaging industry leaders to lean into hypersonic technology. Furthermore, the Congressional Research Service published a report in March on hypersonic weapons—including developments made by the U.S., Russia and China—and critical issues for Congress to consider as it reviews the Pentagon’s plans for U.S. hypersonic weapons programs.

In response to the AUKUS announcement, China voiced concerns about sparking an arms race. Chinese Foreign Ministry spokesperson Zhao Lijian said that the AUKUS agreement “not only increases nuclear proliferation risks and brings shocks to the international non-proliferation system, but also intensifies [the] arms race and undermines peace and stability in the Asia-Pacific.” Song Zhongping, a military expert writing for The Global Times, took Zhao’s stance even further, stating that AUKUS is a “military alliance that spans three oceans” and that this pact “will further intensify the global arms race” and “will also seriously affect the balance of regional military strength.”

 For Australia and the U.K., the recent announcement demonstrated the strength of the AUKUS alliance and its development. Australian Prime Minister Morrison said that the agreement supports AUKUS’s goal of enhancing Australia’s military capability and that it “is in the best form that can be working with our partners.” Stephen Lovegrove, the U.K.’s national security adviser, said that “in light of Russia’s invasion of Ukraine, it’s more important now than ever that allies work together to defend democracy, international law and freedom around the world.”

Japan Takes Security Measures

In an interview with Kyodo News in early April, Japanese Defense Minister Nobuo Kishi stated that the defense ministry will consider requesting a larger budget for the next fiscal year to strengthen Japan’s defense capabilities, and will also consider a controversial plan that would allow Japan to acquire offensive “enemy base strike capabilities,” which would mark a departure from the country’s exclusively defense-oriented policy. These considerations are in response to an increasingly restless regional security environment, which include China’s continued militarization in the Indo-Pacific region, North Korea’s renewed missile and nuclear threats, and Russia’s invasion of Ukraine.

Japan has taken several security measures in response to increasing Chinese military activity in the region, including four Chinese Coast Guard ships sailing in Japanese waters off the Senkaku Islands in the East China Sea for about two hours on March 16. In early April, the Japan Air Self-Defense Force repositioned a mobile radar unit to Yonaguni Island on its southern island chain, closer to Taiwan, to strengthen defenses. Furthermore, the Japan Maritime Self-Defense Force commissioned the first of a planned fleet of 22 Mogami-class multirole frigates in late March, which will replace the fleet’s aging Abukuma-class destroyer escorts and Asagiri-class light destroyers. This new frigate class, which will be used for surveillance missions in Japan’s surrounding waters, will have a low radar signature and will deliver new capabilities, including a vertical launch system hosting surface-to-air missiles for medium-range anti-air warfare capability, and the ability to conduct anti-mine warfare operations.

Japan has also significantly expanded its joint drills and training with the U.S. and other partners such as Australia, India, France, Britain and Germany. In late March, Japan’s parliament approved a new agreement with the U.S., supporting a 1.05 trillion yen ($8.6 billion) budget to host U.S. troops. The budget would cover advanced arsenals used in joint military exercises, as well as utilities and facilities used on American bases in the country. Japan’s Maritime Self-Defense Force also joined forces with the U.S. Navy and the Royal Australian Navy to conduct trilateral training in the South China Sea, which concluded on March 15. In mid-March, Japanese and U.S. Marines also held training together near Mt. Fuji, practicing landing and combat operations, a signal of increased military cooperation between the two allies.

On the political front, Japan in the past month has also engaged in discussions with regional allies to strengthen cooperation around security in the South China Sea. In March, Japanese Prime Minister Fumio Kishida and Indian Prime Minister Narendra Modi discussed the security challenges in the South China Sea and acknowledged the growing space for cooperation in the Indo-Pacific region. In April, Japan and the Philippines held meetings, in which they agreed to work toward signing a treaty designed to facilitate joint exercises and strengthen defense cooperation in response to China’s increasingly assertive moves in the region.

The Philippines

From March 28 to April 8, the U.S. and Philippine armed forces conducted the 37th iteration of Joint Exercise Balikatan. Described by U.S. Indo-Pacific Command as Balikatan’s “largest ever” annual iteration, the two-week-long Philippine-led exercise involved approximately 8,900 military service members from both countries and focused on maritime security, amphibious operations, live-fire training, urban operations, aviation, counterterrorism, and humanitarian assistance and disaster relief. The aircraft carrier USS Abraham Lincoln (CVN-72) arrived in Manila for a port visit just prior to the start of Joint Exercise Balikatan after conducting operations in the South China Sea, and the Expeditionary Support Base USS Miguel Keith (ESB-5) arrived in the area to participate in the exercise. The USS Miguel Keith’s presence in the South China Sea drew the attention of Chinese state-run news outlet the Global Times, which described it as a “worrying signal” of provocative moves by the U.S. military. A spokesperson for the U.S. Embassy in the Philippines described Balikatan (Tagalog for “shoulder-to-shoulder”) as a “critical opportunity to work … with our Philippine allies toward a free and open Indo-Pacific.”

The full-scale revival of Balikatan following years of cancellation or downscaling during the coronavirus pandemic signals the continued strength of the two nations’ security relationship despite some cooling during the Trump and Duterte administrations. The Philippines will elect a new president to replace Rodrigo Duterte next month, and some presidential candidates have argued for a firmer stance against Beijing’s territorial claims in the South China Sea. Duterte, however, has reminded his potential successors of a memorandum of understanding (MOU) between China and the Philippines signed in 2018 (following China’s rejection of the South China Sea Arbitration’s affirmation of exclusive Philippine rights to its EEZ and continental shelf), which instead allows both countries to exploit oil and gas resources in the contested area and does not address the issue of sovereignty. 

Duterte cautions that his successor should abide by the MOU or expect conflict with China. In light of the upcoming election and the large-scale joint military exercise with the U.S., China’s Foreign Minister Wang Yi has cautioned the Philippines to avoid “disturbances” to its China policy that might damage the stability of the South China Sea. Despite these cautionary statements, the Philippines has frequently protested Beijing’s aggressive actions in the region, most recently a Chinese Coast Guard vessel’s “close distance maneuvering,” which allegedly resulted in a near-collision with a Philippine vessel towing a survey cable to inspect undersea fault lines in the disputed Scarborough Shoal (Chinese: Huángyán Dǎo; Filipino: Panatag Shoal). Last month, Manila also protested a Chinese People’s Liberation Army Navy (PLAN) Dongdiao-class electronic reconnaissance ship’s “lingering presence” within Philippine archipelagic waters. The challenged PLAN vessel alleged that it was exercising innocent passage through archipelagic waters in accordance with UNCLOS Article 52. However, UNCLOS Article 17 generally requires innocent passage to be “continuous and expeditious,” and the PLAN vessel remained in Philippine archipelagic waters for three days despite repeated challenges by the Philippine Navy. The Philippines Department of Foreign Affairs concluded that the PLAN vessel’s actions did not constitute innocent passage and summoned the Chinese ambassador to demand that China respect Philippine sovereignty and comply with its obligations under international law. Manila has filed more than 241 diplomatic protests against China since 2016—183 were filed in 2021 alone.

The Philippines has also increased its security cooperation and transfers of equipment and technology with Japan, a nation with whom it shares concerns about China’s assertive actions in support of its disputed territorial claims in the region. During an April meeting in Tokyo, defense ministers from both countries affirmed the importance of maintaining a “free and open Indo-Pacific” and, in a veiled reference to China, condemned unilateral changes to the status quo.


Amid growing concern over Russia’s invasion of Ukraine, a senior defense official testified that the U.S. response to China moving to take over Taiwan would be different from its reaction to Russia’s invasion of Ukraine. Ely Ratner, assistant secretary for Indo-Pacific security affairs, stated that there were a number of security agreements between Taipei and Washington that differ from agreements between the U.S., NATO, and Ukraine, suggesting a different military response.

Against this backdrop, the U.S. recently approved the sale of $95 million worth of arms and equipment to Taiwan to help it strengthen its defense capabilities. The sale would involve equipment, training and other items that would help Taiwan maintain its U.S.-made Patriot Missile Air Defense System. The U.S. Defense Security Cooperation Agency stated that the Taipei Economic and Cultural Representative Office in the U.S. made the request, and the sale served “US national, economic, and security interests.”

The agreement drew quick criticism from China. Chinese Foreign Ministry spokesperson Zhao Lijian said the sale “seriously [violates] the one-China principle and the three China-U.S. joint communiques, … gravely [undermines] China’s sovereignty and security interests, and severely [harms] China-U.S. relations and peace and stability across the Taiwan Strait.”

Taiwan, however, thanked Washington for the approved sale, and the deal will take effect in May. This would be the third arms package to Taiwan under President Biden’s administration, with the most recent arms sale occurring in late February of this year.


The Center for Strategic & International Studies (CSIS) published research indicating that profits from China’s shipbuilding industry are likely offsetting the cost of its naval upgrades. Merchant fleets are growing quickly in response to rising demand, and one single Chinese state-owned enterprise, China State Shipbuilding Corporation (CSSC), holds almost a quarter of the global shipbuilding market. China’s military-civil fusion strategy, in which CSSC plays a key role, aims to eliminate barriers to information transfer between its civilian/commercial sector and military/defense sector in order to apply technological innovations toward simultaneous advancement of both its military and other instruments of national power. By buying merchant ships from CSSC, leading democracies may be inadvertently providing funds and technology that contribute to China’s military advancement. CSIS concludes that U.S. policymakers should pursue options to incentivize foreign companies away from China’s shipbuilding industry and steer them instead toward alternatives in Japan and South Korea.

RAND researchers recently analyzed open-source material and held a workshop with more than 90 U.S. interagency and U.S. Department of Defense participants to analyze Chinese gray zone tactics––coercive geopolitical, economic, military, and cyber and information operations (cyber/IO) activities that go beyond normal diplomatic activity but are below active warfare. The researchers found that China views competition in the gray zone. The report found that gray zone tactics promote pursuit of China’s objectives in the Indo-Pacific by balancing its desire to “alter[] the regional status quo in its favor with a desire to act below the threshold of a militarized response from the United States or China’s neighbors.” By combining geopolitical, economic, military, and cyber/IO activities, China can apply nonmilitary pressure before resorting to military action. The report also noted that China appears to exercise greater caution in using high-profile gray zone tactics against countries like Japan and India than Taiwan. China’s use of gray zone tactics will likely increase as it becomes more active in expanding its influence. Among the gray zone tactics most problematic for the U.S. include China’s support for adversaries and rival countries and its use of economic assets to advance disputed territorial claims.

At The Diplomat, Erick Nielson Javier argues that the Philippines should move toward a more active deterrence posture against China. The article notes that “[t]he prerequisite metrics and theories that would make Philippine deterrence credible” are “absent from the discussion.” Defense officials, including then-Chief of Staff Gen. Cirilito Sobejana have attempted to change the Philippines’ approach to deterrence from a reactive approach––facing aggressors once hostile acts are already underway––to a proactive approach of dissuading aggression. This approach leads the Philippines to lean on allies instead of building indigenous capabilities, an approach that Philippine Secretary of Foreign Affairs Teodoro Locsin seems to recognize is flawed. Overreliance on U.S. power may contribute to a perceived inequality from the Philippine perspective, and liability from the U.S. perspective. Importantly, the article argues, Manila must develop a “theory of victory” to guide its use of its defense resources, such as preserving Philippine holdings in disputed waters. Developing such a theory could also help support the Philippine’s naval modernization efforts by interrogating the logic of procuring systems such as submarines. 

At the German Marshall Fund, Jessica Drun and Bonnie S. Glaser catalog China’s efforts to reinterpret U.N. General Assembly Resolution 2758, which transferred the Republic of China’s seat on the Security Council to Beijing. Drun and Glaser argue that these moves are aimed at restricting Taiwan’s access to the institutions of the U.N.

War on the Rocks published an article by Nozomu Yoshitomi describing the current U.S. and Japanese security posture within the first island chain and described ways in which the two nations could fortify this posture in order to deter a Chinese invasion of Taiwan. It begins with the premise that Beijing would require access further into the Pacific Ocean, and the most direct passages are through the southwest Japanese islands north of Taiwan or through the Luzon Strait between Taiwan and the Philippines. The author predicts that in the event of conflict, these two routes would be exposed to “fierce [People’s Liberation Army] attack to secure air and naval passages.” The U.S. Marine Corps recently announced a plan to develop three Marine Littoral Regiments (MLR) in the Indo-Pacific region in order to further the concept of expeditionary advanced base operations. The primary focus of the MLR is to support sea control by the U.S. Navy and act as a countermeasure against China’s anti-access/area denial capability. Each Marine Littoral Combat Team within the MLR will consist of three infantry companies and an anti-ship missile battery. As the passages north and south of Taiwan are suitable for advanced base operations, but three MLRs will not be sufficient to close all sea-denial gaps, the author recommends that Japan also focus on developing a robust expeditionary advanced base capability similar to the MLR. 

The security posture in the Luzon Strait is weaker than the Japanese southwest islands due to the Philippines’ limited capability for air defense, anti-submarine warfare and electromagnetic warfare. The author recommends that the U.S. Marine Corps prioritize its limited MLR resources in the Luzon Strait, provided that Japan fortifies the southwest islands against Chinese invasion and rapidly develops its own expeditionary advanced base capability similar to the MLR. The article concludes that fortifying the sea-denial capability within the passages north and south of Taiwan will greatly impact China’s intent and capability to conduct an invasion of Taiwan.

Teresa Chen is a J.D. student at Harvard Law School. She holds a bachelor’s degree in Global Affairs from Yale University.
Alana Nance is a J.D. student at Harvard Law School. She holds a bachelor’s degree in Chinese from the U.S. Naval Academy and served as an officer in the U.S. Marine Corps.
Han-ah Sumner is a second-year J.D. student at Harvard Law School. She holds a bachelor’s degree in Ethics, Politics and Economics from Yale University.

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