The U.S.–Japan Security Alliance Must Act Now to Deter China from Attacking Taiwan

Report Asia

The U.S.–Japan Security Alliance Must Act Now to Deter China from Attacking Taiwan

April 29, 2022 30 min read Download Report
Bruce Klingner
Senior Research Fellow, Northeast Asia
Bruce Klingner specializes in Korean and Japanese affairs as the Senior Research Fellow for Northeast Asia.


Japan’s rhetoric about and action on assuming a larger security role in the Indo–Pacific have been positive and significant. Tokyo’s willingness to call out Chinese belligerence and advocate solidarity with Taiwan are commendable. Japan’s economic response to Russia’s invasion of Ukraine was quick and forceful, portending a similarly robust reaction to Chinese aggression against Taiwan. For the near term, Japan will maintain strategic ambiguity, as will the United States, on whether and to what degree it would defend Taiwan. In Japanese policymaking, the prologue to effective coordination with the U.S. often lasts an exceedingly long time—so the U.S.–Japan security alliance must start now to convince Beijing every day that “today is not the day” to attack Taiwan.

Key Takeaways

China’s escalating intimidation of its neighbors, particularly Taiwan, has provoked uncharacteristically bold statements from Japan.

Japan has demonstrated its increasing importance to the U.S. in countering China’s threats to Taiwan, and the foundation for effective responses must be laid now.

Japan and the U.S. should remove Japanese impediments to rapid action and delineate roles, missions, and capabilities for Taiwan-related contingencies.

Russia’s second invasion of Ukraine on February 24, 2022, was a brutal reminder of the potential for authoritarian countries to attack smaller countries on their periphery. Moscow’s assault should also be a catalyst for enhancing deterrence against Chinese expansionism in the Indo–Pacific region.

China has stepped up its intimidation strategy against its neighbors in both the East and South China Seas. Japan has responded by issuing uncharacteristically bold statements criticizing Beijing’s threats against Taiwan, as well as engaging in bilateral military contingency planning with the United States. Japan’s actions are consistent with its stated desire to assume a larger regional security role.

Japan has demonstrated that it is an increasingly important security partner to the U.S. in countering China’s attempts to intimidate its neighbors. Tokyo has been studying its possible military responses to a Chinese attack on Taiwan, including protecting any U.S. warships and military planes that come to Taiwan’s defense. Japanese military support would be a critical piece of a U.S. response. But questions remain about the extent of Japanese support in a defense of Taiwan and which role its Self-Defense Forces (SDF) would play in a Taiwan contingency.

While Japan has significantly enhanced its military capabilities in recent years, the SDF will potentially be constrained by operational shortcomings as well as by numerous constitutional, legal, and political constraints.1 In addition, Japanese decision-making is notoriously slow, even in times of crisis.

China’s escalating threats against Taiwan, and its rapidly increasing military capabilities, require that the United States and Japan get ahead of these challenges and enhance ongoing coordination of potential responses. Tokyo and Washington should work together to resolve the labyrinth of Japanese impediments to rapid action, as well as clearly delineate bilateral roles, missions, and capabilities for Taiwan-related contingency operations. Establishing the foundation for effective responses should be done now rather than during a crisis.

Japanese Views of the Looming China Threat

For years, Japanese security officials were anxious about the growing Chinese threat but avoided public discussion, instead referring euphemistically to “maintaining northeast Asian stability.” That changed as Tokyo became increasingly alarmed by China’s surging defense expenditures, rapidly expanding and modernizing military capabilities, and escalating aerial and maritime incursions into Japan’s territorial waters and contiguous areas.

Japan’s 2021 defense white paper described these and other recent Chinese military developments as “a matter of grave concern,” while stating that Beijing’s unilateral assertions over Japan’s territorial waters around the Senkaku Islands are “a violation of international law.”REF Japanese Defense Minister Nobuo Kishi declared that the Chinese are seeking to “change the status quo unilaterally backed by force and coercion. And they’re trying to make it into a fait accompli.”REF

While Japan was initially concerned only with Chinese incursions into the East and South China Seas, Tokyo has more recently focused on a potential Taiwan crisis. Beijing has stepped up its threats and pressure on Taiwan, including sending fighter jets and naval ships around the island.

Senior U.S. military officials share these concerns. Admiral Philip Davidson, then–Commander of United States Indo–Pacific Command, testified that China’s “rapidly advancing capabilities and increasingly competitive posture underscore its drive to become a regionally dominant, globally influential power” and postulated that Beijing will have the capability to seize Taiwan “in the next six years.”REF Admiral John Aquilino, Davidson’s successor, commented that a military takeover of Taiwan was the top concern for Indo–Pacific Command.REF

Japan increasingly sees the potential to be drawn into a U.S.–China conflict over Taiwan. At their closest point, Japan’s southwest islands and Taiwan are only 70 miles apart. Japan could be drawn into a Taiwan conflict either indirectly, given its proximity, or directly if China were to attack U.S. bases in Japan being used as staging points to defend Taiwan. A March 2022 poll showed that 77 percent of Japanese respondents were concerned over the risk of a Taiwan crisis spilling over to affect Japan.REF

Former Prime Minister Shinzo Abe assessed that China could not attack and conquer Taiwan without violating or attacking Japanese territory, territorial waters, or airspace. He commented that it is likely that any Chinese action against Taiwan would also constitute an armed attack against Japan.REF

Japan’s New Rhetorical Boldness on Defending Taiwan

The deteriorating security environment and China’s increasing military pressure against Taiwan have spurred Tokyo to risk Beijing’s wrath by issuing increasingly bold public statements of support for Taipei. There is a new senior-level willingness to align Japan’s national interests with protecting Taiwanese security, even hinting at military support during hostilities.

Japan and Taiwan have a strong diplomatic and economic relationship. Taiwan is a major Japanese trading partner as well as a major global supplier of semiconductors and electronics. A large number of Japanese live in Taiwan.

In his April 2021 summit meeting with President Joe Biden, then–Prime Minister Yoshihide Suga affirmed the “importance of peace and stability across the Taiwan Strait” and “the peaceful resolution of cross-strait issues.”REF It was the first reference to Taiwan in a U.S.–Japan summit document since 1969. Notably, Suga was willing to criticize China by name for its belligerence in Asia, something that South Korean President Moon Jae-in refrained from doing in a joint statement with President Biden a month later. A Japanese poll after the summit meeting showed that 74 percent of the Japanese public supported Suga’s affirmation of support for Taiwan.REF

However, Suga subsequently appeared to walk back hints of military support. He told the Japanese legislature that the joint statement “does not presuppose military involvement.” Suga demurred that, rather than making a sweeping pledge, Tokyo would first need to consider all aspects of a given situation before reaching a final decision about military involvement.REF

Defense Minister Nobuo Kishi visited Japan’s Yonaguni Island, less than 70 miles from Taiwan, in April 2021 to emphasize that the proximity to Taiwan had implications for Japanese security. He later declared that the “peace and stability of Taiwan are directly connected to Japan.”REF

Deputy Prime Minister Taro Aso more forthrightly declared that Japan would participate in the defense of Taiwan. He asserted that a Chinese invasion would be an “existential threat [to Japan] since Okinawa could be next” and would necessitate a joint Japanese–U.S. response to defend the island.REF Similarly, former Prime Minister Abe declared that “a Taiwan emergency is a Japanese emergency, and therefore an emergency for the Japan–U.S. alliance.”REF

Prime Minister Fumio Kishida declared that countering China is Japan’s “top priority”REF and called Taiwan “the front line in the struggle by democracies to resist authoritarianism’s advance.” Kishida advocated that Tokyo and Washington run joint crisis simulations addressing Taiwan crisis contingencies.REF Such comments marked a shift for Kishida, who had previously described himself as a “dove” in contrast to Prime Minister Abe’s hawk.REF

Japan mentioned the importance of stability in the Taiwan Strait for the first time in its 2021 annual defense white paper. Tokyo emphasized that “the stability of the situation surrounding Taiwan is important for the security of Japan and the stability of the international community. [Japan must] pay close attention to the situation with a sense of crisis more than ever before.”REF

Strong Words, But No Policy Changes Yet

Japan’s bolder public statements represent a significant evolution in Japanese foreign policy, but it remains unclear whether they also reflect a change in policy. Tokyo may have changed rhetorically, but not yet operationally. There likely remain significant differences amongst what Japan can do, what it implies it will do, and what it will do. As yet, there have been no declared policy changes nor a pledge to directly intervene in a military conflict to defend Taiwan, or even to allow a U.S. defense of Taiwan from bases in Japan.

That said, Tokyo seems to be moving toward a stronger position on taking some security action to assist in the defense of Taiwan. The public statements could be laying the initial groundwork for convincing the legislature and public of the necessity for Japanese actions to deter or respond to Chinese aggression against Japan. But any shift likely portends lengthy debate, incremental policy changes, and a necessity to overcome inherent public resistance to altering the status quo.

Policy Context: Real Changes

Japan has made some critical changes to policies that underlie the U.S.–Japan alliance. In 2015, Japan passed the Legislation for Peace and Security to enable the country to play a more comprehensive role in responding to global security challenges. The defense reform legislation allowed Japan to exercise collective self-defense, which enables a nation to regard an attack on another nation as an attack on its own territory, even if it itself is not directly attacked. Previously, Tokyo had stipulated that Article 9 of its war-renouncing constitutionREF precluded Japan from engaging in collective self-defense.

The legislation eased restrictions on the SDF, enabling greater flexibility, responsiveness, and interoperability with other nations for training, exercises, and planning.

The defense legislation:

  • Eliminated geographic constraints by substituting a situational threshold (situations that “gravely affect the peace and stability of Japan”) rather than limiting support to “Situations in Areas Surrounding Japan.”
  • Authorized support to non-U.S. troops. Japan can now provide greater logistical support to friendly countries to collectively address situations that threaten international peace and security, although not where combat activities are being conducted.
  • Expanded the range of allowable logistical support, such as refueling fighter planes and transporting ammunition for U.S. and other foreign military forces in multinational operations.
  • Allowed the SDF to protect friendly nations’ military assets. The SDF can now defend military assets, including warships of the U.S. and “a foreign country in a close relationship with Japan.”REF

The subsequent Guidelines for U.S.–Japan Defense CooperationREF (“alliance guidelines”) called on Japan to provide logistical support on the high seas and international airspace around Japan and to other military forces besides those of the United States. Japan is also allowed to protect U.S. forces and assets, such as ships, from attack by mutual enemies.

To a greater degree than previous U.S.–Japan defense guidelines, forces from both countries are now able to engage in more integrated operations, such as for missile defense; antisubmarine warfare; maritime security; maintaining safe and secure sea lines of communication; minesweeping; counterpiracy, counterterrorism, and counterproliferation measures; and intelligence, surveillance, and reconnaissance (ISR) operations. Japan could also cooperate more actively through multilateral security networks with Australia and India.

These are all commendable, necessary steps, but not sufficient for operationalizing the alliance in the event of a Chinese attack on Taiwan.

Decision-Making Obstacles to Japanese Involvement

While the 2015 defense legislation lowered the threshold for Japanese security action beyond its shores, it remains uncertain whether Tokyo would actually take such action. Whether the habitually slow Japanese decision-making process could respond expeditiously during a crisis is also in doubt.

A Japanese decision to intervene in a Taiwan crisis would be hindered by constitutional, legal, and political constraints. Deliberations would depend heavily on the circumstances of the situation and a prime minister willing to intervene. Potential factors include whether Taiwan was being attacked or blockaded, whether Japan’s southwest islands were threatened, and the extent of international support for Taiwan’s defense. It is not known which impact a Chinese pledge to not attack Japan if Tokyo refused to allow U.S. forces to support Taiwan would have on Japanese decision-making.

A decision to intervene would then require the government overcoming legislative and public resistance. The ruling Liberal Democratic Party’s pacifist coalition partner Komeito would likely resist direct military involvement. The Japanese populace remains highly risk-averse and casualty-averse, as well as deeply suspicious of the use of the military as a policy tool. While the populace supports Japan’s stronger statements of support for Taiwan, that does not equate to advocating that Japan adopt a more offensive security posture or assume a greater security role in the region.

Japan Must Play a Role in Defense of Taiwan

The United States would play the predominant role, other than Taiwan itself, in responding to a Chinese attack on Taiwan. However, Washington could not effectively come to Taiwan’s defense without the use of U.S. forces in Japan as well as significant Japanese logistic and operational support. To respond to Chinese aggression against Taiwan, Washington would need Japan to rapidly grant permission to allow U.S. forces to operate from bases in Japan.

The U.S.–Japan mutual defense treaty states: “For the purpose of contributing to the security of Japan and the maintenance of international peace and security in the Far East, the United States of America is granted the use by its land, air and naval forces of facilities and areas in Japan.” However, Washington must first engage in prior consultation to receive Tokyo’s acquiescence to operate, from bases in Japan, in combat operations other than the defense of Japan.

Japanese agreement risks making those U.S. bases, as well as Japan itself, the targets of Chinese attack. However, refusal by Tokyo would undermine U.S. ability to effectively respond to a Chinese attack on Taiwan. If Japan willfully stood idly by when its forces could have protected U.S. territory or forces from deadly attack, it could do irreparable damage to its alliance with the U.S. If Tokyo failed to come to Taiwan’s assistance after publicly linking its national security to that of Taiwan, it would tarnish Japan’s reputation.

To determine the extent of its support for Taiwan, Tokyo would apply the Armed Attack Situation Response Law,REF which grants authorities and delineates responsibilities of national and local governments when reacting to adverse security situations. The law defines such situations as:

  • Events that will have a significant impact on the security of Japan and its people, including an emergency and other situations that, if left without response, could lead to a direct armed attack on Japan. The “Law Concerning Measures to Ensure the Peace and Security of Japan in Situations that Will Have an Important Influence on Japan’s Peace and Security”22 aims to strengthen cooperation with foreign countries in a common response.
  • “Survival-threatening situations” where an armed attack against a foreign country that is in a close relationship with Japan occurs, which in turn poses a clear risk of threatening Japan’s survival and of fundamentally overturning the Japanese people’s rights to life and liberty.
  • Armed attacks against Japan from outside, or imminent and clear danger of an armed attack.REF

An attack on Taiwan could be the precursor to an attack on Japan but, as things currently stand, until such an attack occurs, Tokyo is hamstrung in the actions it can undertake. If China did not directly attack U.S. forces in Japan or Japanese facilities, Tokyo could designate a Taiwan crisis as a “significant impact situation” or “survival-threatening situation.”

In an “important influence situation,” Japan could conduct coordinated ISR operations and provide rear-area support, including logistics (for example, supply, repair and maintenance, communications, transportation, refueling, and medical services); protection of U.S. bases in Japan; refugee relief operations; search and rescue operations; minesweeping; noncombatant evacuation operations; and protection of military and civilian craft outside the combat area. SDF operations would take place in Japanese territory or surrounding environs but not within the territorial airspace or waters of another country nor where combat operations are taking place.REF

A survival-threatening situation would provide the SDF with additional authorities to exercise collective self-defense, including defending U.S. forces. However, such a designation requires the government to produce a Basic Response Plan which lists all potential SDF operations. The plan must also credibly demonstrate that three conditions have been met: (1) Japan’s own survival must be under threat, there are no other means available to resolve the situation, and whatever force it uses must be the minimum possible;REF (2) the plan must be approved by the cabinet and then the Diet, and SDF operations not included in the approved plan are proscribed; and (3) the SDF must avoid integration with the forces of a foreign country and must not conduct activities where combat is taking place.REF

If China attacked Japan or U.S. forces in Japan, or Japan’s territorial waters or airspace, the SDF could engage in combat operations to defend Japan and engage in collective self-defense actions to protect U.S. or other foreign forces. Japan would have primary responsibility for repelling an armed attack on, or invasion of, Japan through counter-air attacks, air and missile defense, maritime defense, and anti-submarine warfare. SDF defensive operations would be limited to Japanese territory and its surrounding waters and airspace.REF

However, the United States may also request that Japan provide armed escorts for U.S. ships and aircraft between Japan and Taiwan as well as combat search and rescue operations.REF Japan could also defend sea lines of communication and conduct island chokepoint control and anti-submarine warfare operations to provide more freedom to maneuver to U.S. vessels.REF

Japan would not directly defend Taiwan nor operate SDF forces on foreign territory. Tokyo would most likely declare an important “influence situation” to enable the SDF to play an important rear-area support role outside combat operations areas to the United States and other nations. Japan’s assumption of rear-area responsibilities could free up U.S. forces for operations closer to Taiwan.

Operational Context: Building Greater Capabilities

Faced with rapidly growing military and asymmetric security threats, Japan:

  • Rebalanced its forces away from Cold War missions in the northern Hokkaido area to counter the Chinese threat to its remote southwest islands. Tokyo acquired new capabilities, built new facilities, deployed new units and augmented others, improved amphibious warfare capabilities, increased air and sea mobility, and enhanced command-and-control capabilities for joint and integrated operations.
  • Deployed new radar sites, surface-to-ship and surface-to-air missile units, and intelligence-gathering and security units on Yonaguni, Amami Oshima, Miyako, and Ishigaki Islands. These units will bolster ISR as well as rapid-response capabilities to protect key maritime chokepoints in the Miyako and Tokara Straits.
  • Planned construction of a new airfield on Mage Island to improve mobility during a crisis as well as serve as a training site for U.S. Navy carrier landing practice and SDF air training.REF
  • Purchased additional F-35s and increased the number of F-15s and E-2D early warning aircraft deployed at Naha Air Base in Okinawa.
  • Acquired longer-range missiles. The air-to-ground missile (AGM)-158B Joint Air-to-Surface Standoff Missile-Extended Range (JASSM-ER) with a range of 900 kilometers and the AGM-158C Long Range Anti-Ship Missile (LRASM) will augment standoff attack capability for aircraft, and the Type 12 and Type 88 surface-to-ship standoff missiles will enhance long-range attack capabilities against ships. The extended range of the ASM-3 air-to-ship missile will provide air defense of the southwest islands.
  • Strengthened the Japanese Coast Guard (JCG) by augmenting the budget, procurement, and deployment of additional units. The JCG has significantly expanded its maritime and aerial patrols near the Senkaku Islands. The JCG improved coordination with the Maritime Self-Defense Force (MSDF) and periodically conducts joint training and exercises for maritime security operations.
  • Established the Amphibious Rapid Deployment Brigade of 3,000 troops to defend or retake remote islands seized by China.
  • Converted the Izumo-class destroyer for F-35s. To compensate for few airfields in the southwest island region from which to project power against Chinese land incursions, Japan converted the helicopter-carrying destroyers to handle F-35B short take-off and vertical landing (STOVL) aircraft. Doing so provides the SDF with greater firepower and mobility in an otherwise isolated region.
  • Purchased C-2 transport aircraft, CH-47 JA helicopters, and V-22 Osprey to support large-scale transport and deployment operations.

Prime Minister Kishida advocates increasing Japan’s defense budget beyond its traditional level of 1 percent of gross domestic product (GDP) and augmenting the country’s missile defenses. He also stated that Japan should consider building a missile-strike capability against Chinese and North Korea missile targets to be implemented in response to initial attacks.REF

Lingering Shortcomings

Japan has developed a formidable military with an impressive array of sophisticated weapons. However, the SDF continues to have significant deficiencies in command-and-control systems and a limited ability to conduct true joint operations amongst its services and combined operations with U.S. forces. When conducting a defense of Japan, the U.S.–Japan alliance guidelines call for bilateral operations to be carried out in a parallel, coordinated manner with each country conducting joint operations of their own services within their own chain of command rather than integrated, combined operations, as would be the case with South Korean forces in a crisis on the Korean Peninsula. The 2015 U.S.–Japan Alliance Guidelines established the Alliance Coordination Mechanism (ACM) to strengthen policy and operational coordination between the U.S. and Japanese militaries.REF However, the ACM remains a coordination process rather than a permanent unified command organization and is insufficient for integrated alliance wartime operations.

The new amphibious brigade lacks organic land, air, and naval assets and is reliant on Japan’s maritime and air self-defense forces, which do not have the equipment to rapidly transport the brigade to the remote southwest islands. Unlike the U.S. Marines, the brigade cannot conduct close-in air support.

The SDF lacks sufficient ammunition and fuel reserves, aerial refueling capabilities, oilers, and underway replenishment ships. As a result, the MSDF’s surface combatants and minesweepers would have a relatively limited operating range.REF

Recent Positive Developments

The bold statements by senior Japanese officials appear to lay the political foundation for support during a Taiwan crisis. Behind the scenes, there appears to be internal Japanese planning and some discussion with U.S. counterparts on contingency cooperation. In March 2021, the U.S. and Japanese defense chiefs agreed to closely cooperate during a Taiwan crisis.REF

Planning. Japan has studied military operations that it could conduct in support of a conflict over Taiwan. Tokyo has assessed possible responses, including releasing a dispatch order to protect U.S. warships and military planes in such a conflict. Japan is evaluating how its security laws could apply in a possible Taiwan-related conflict and seeking to clarify SDF activities.REF

The U.S. and Japanese militaries reportedly drafted a combined operation plan that would enable the establishment of U.S. Marine Corps attack bases on Japan’s southwest islands during a Taiwan contingency. Under the plan, the Marines would deploy high-mobility artillery rocket systems to a temporary base while the SDF provided logistical support of ammunition and fuel.REF

Training. Since 2019, Japan and the United States have conducted strategic-planning and combined exercises in preparation for a possible conflict. The eventual goal could be to create an integrated war plan for a Taiwan war that threatens Japan’s security.REF

  • December 2021–Exercise Yama Sakura 81 was the largest bilateral and joint command post exercise in its 40-year history. The multi-domain exercise included units from the U.S. Army, U.S. Marine Corps, and Japanese Ground SDF, as well as a small Australian contingent.REF
  • December 2021–Exercise Resolute Dragon was one of the largest joint military exercises conducted between the U.S. and Japan. U.S. Marines and Japanese counterparts, along with the U.S. Navy, tested the U.S. Marine Corps’ new Expeditionary Advanced Basing Operations (EABO) concept in which it sets up multiple smaller, easily built bases. The exercise rehearsed how American and Japanese chains of command would be integrated and structured while conducting joint operations.REF
  • February 2022–Exercise Noble Fusion was a joint and combined naval expeditionary exercise combining multiple elements of the U.S. Navy, Marine Corps, and Air Force alongside the Japan Maritime and Ground Self-Defense Forces in the Philippine Sea. The exercise focused on countering aggressive actions by adversaries in the first island chain with lethal sea-denial operations, seizing key maritime terrain, and securing freedom of movement.REF

In a Taiwan crisis, the United States would need Japan to quickly determine the roles and missions its Self-Defense Forces would conduct to augment American assistance to Taipei. This would require a rapid decision by the prime minister and expeditious approval by the cabinet and legislature. Japan should provide expansive rear-area support as well as implement collective self-defense if U.S. forces or bases were to come under attack.

Recommendations for Japan and the United States

Recommendations fall into four broad categories: (1) improving allied military capabilities; (2) enhancing U.S.–Japan policy coordination and implementation; (3) augmenting the dialogue with Taiwan; and (4) increasing regional coordination for a Taiwan contingency.

1. Improving Allied Military Capabilities. To improve its military capabilities, Japan should:

  • Incorporate Taiwan contingency into future defense documents. The Kishida administration indicated it would revise Japan’s 2013 National Security Strategy and the 2018 National Defense Program Guidelines (NDPG) and Medium-Term Defense Program (MTDP). The forthcoming documents should more comprehensively discuss the importance of Taiwanese security to Japan’s national strategic interests. The documents should delineate Japan’s threat assessment, security strategy, and potential roles and policies, including its relationships with regional partners. The NDPG and MTDP should identify procurement and deployment decisions to enable sufficient crisis responses.
  • Increase its defense budget. A dramatically escalating threat environment requires a commensurate response by Japan. Tokyo must modernize its defense capabilities by augmenting air, naval, and missile defense forces; amphibious warfare capabilities; and increasing airlift and sealift assets. Doing so requires Japan to abandon its past practice of minor incremental defense increases and instead work toward spending the same 2 percent of GDP on defense to which NATO members have committed. Prime Minister Kishida has pledged to move beyond the current arbitrary cap of 1 percent but must implement significant increases in defense spending in forthcoming budgets.
  • Develop retaliatory enemy-base attack capabilities. Tokyo’s acquiring of strike capabilities to reduce missile strikes against Japan and U.S. forces would augment allied deterrence and defense capabilities. However, Japan and the U.S. will need to work together to overcome numerous constitutional legal, budgetary, technical, and bureaucratic obstacles. Such decisions should be made in an alliance framework, in part to allay South Korean concerns that would inevitably arise.REF
  • Create a Japanese joint task force or regional command for the southwest islands with a unified commander. Having disparate services carrying out missions in parallel rather than in an integrated structure could prove disastrous in a conflict. The new Amphibious Rapid Deployment Brigade can be a catalyst for joint doctrine, procurement, training, and operations.
  • Discuss hosting U.S. intermediate-range non-nuclear missiles at bases in Japan. Since a permanent deployment could be politically contentious, Washington and Tokyo should consider adopting a prior agreement for rapidly deploying these missiles during crisis contingencies. All legal and operational issues that could constrain deployment should be resolved during peacetime.

2. Enhancing U.S.–Japan Policy Coordination and Implementation. A Taiwan contingency could unfold quickly. Military operations require planning, practicing, redeployment, and logistical replenishment. An effective allied response requires quick policy decisions and implementation. A crisis is not the time for assessing legal response parameters or determining organizational responsibilities. Delays in implementing operational plans can have deadly or even disastrous results.

Much of the U.S.–Japanese planning will need to be done behind the scenes due to maintaining operational security, both countries’ strategic ambiguity toward Taiwan, and the sensitivity of Taiwan in U.S.–China relations. There is a dichotomy between announcing planned responses to serve as a deterrent and maintaining silence so as to not incite a strong Chinese response.

To enhance their policy coordination and implementation, the U.S. and Japan should:

  • Expand ongoing bilateral discussions and operational planning. The two countries should do so on a whole-of-government basis across ministries, agencies, and departments rather than only including both countries’ militaries. Bilateral contingency exercises to test agreed upon plans are necessary to identify decision points, unclear lines of authority, and potential shortfalls and impediments to rapid implementation—and to then take action to remedy them.
  • Remove political impediments to action and coordinate military contingency plans and develop common operational concepts. Washington should articulate its expectations of Japan’s roles, while Tokyo should define the operational measures it is willing to take—and not willing to take—in the defense of Taiwan. As Dwight D. Eisenhower famously said, “In preparing for battle I have always found that plans are useless, but planning is indispensable.”
  • Expedite Japan’s habitual slow decision-making during Taiwan crisis contingencies. It would also be useful if the SDF and U.S. Department of Defense pre-brief Diet members on potential courses of action, the legal authorities for doing so, and the repercussions for Japanese security and its alliance with the United States if Tokyo were to eschew support for defending Taiwan.
  • Align allied plans to counter China’s anti-access and area-denial (A2/AD) strategy. Japan should closely coordinate its defense plans with emerging U.S. Army and Marine Corps strategies, which may significantly alter U.S. doctrine, strategy, procurement, and deployment plans in the Indo–Pacific theater. Japanese and U.S. alliance managers should identify complementary roles and missions, not only for defense of Japan but also for a broader regional strategy.
  • Improve alliance military coordination. The lack of a unified U.S.–Japan command constrains combined operations. However, Washington and Tokyo can implement several measures to enhance the interoperability and integration of military operations, such as:
    • Enhancing the Alliance Coordination Mechanism from an ad hoc process into a permanent operationally capable joint and combined planning, crisis management, and command structure.
    • Updating bilateral operational plans with deeper consideration of Taiwan contingencies. The U.S. and Japan should synchronize military plans and align bilateral roles, missions, and capabilities.
    • Expanding bilateral military exercises of increasing scope and complexity to include Taiwan-related situations. These should include rapidly moving forces to Japan’s southwest islands.
    • Increasing training with regional partners. A recent Japan–Australia reciprocal access agreement facilitates bilateral training exercises in both countries.

3. Augmenting the Security Dialogue with Taiwan. To augment the U.S. and Japanese security dialogue with Taiwan, the U.S. and Japan should:

  • Explore ways to increase communication and coordination on contingencies with Taiwan. While direct senior-level political and military contact with Taipei could be unnecessarily provocative, given Beijing’s allergy to any expanded Japanese military role especially regarding Taiwan, both countries’ coast guards and air traffic control authorities could be used as a proxy for coordinating maritime and aerial surveillance and reconnaissance, situational awareness, and real-time intelligence exchanges of Chinese military movements in the East China Sea.
  • Enhance bilateral military communication links to enable rapid crisis response to Chinese incursions. Currently, SDF military communications operators in Okinawa cannot communicate directly with Taiwanese authorities.REF The Japanese Ministry of Defense in Tokyo has no one who is formally tasked with managing the relationship with Taiwan.REF The U.S. and Japan should also work on expanding trilateral intelligence-sharing and contingency-planning with Taiwan.

4. Increasing Regional Coordination for a Taiwan Contingency. An international response to Chinese attacks on Taiwan would not necessarily be restricted to the Taiwan area-of-operations but could target Chinese interests in a far broader geographic area.

Japan could deny China’s freedom of navigation through straits in the first island chain while regional partners, such as Australia, could interdict Chinese military and commercial transit in the South China Sea. Australian Defense Minister Peter Dutton stated “it would be inconceivable” for Australia not to join the United States should Washington take action to defend Taiwan.REF Impeding Chinese maritime trade routes would be done in conjunction with extensive international sanctions and punitive trade restrictions.

To increase regional coordination for a Taiwan contingency, Japan should:

  • Enhance security cooperation with other nations that uphold the rule of law and protect sovereignty. For several years, Tokyo has been upgrading and expanding security relations with regional and European partners, including Australia, France, Germany, India, and the United Kingdom. Future cooperation and military exercises could quietly incorporate Taiwan contingencies.
  • Explore joining the Australia–United Kingdom–United States (AUKUS) quadrilateral security pact. Such a development would further deepen diplomatic, security, and defense cooperation in the Indo–Pacific region, as well as more closely link Japan with like-minded democracies. An expanded security pact need not include the nuclear submarine component of the AUKUS since Japan’s maritime operational requirements do not require long-range nuclear submarines. However, there could be multilateral cooperation on research and development of missiles, drones, and aircraft.


Japan’s rhetoric and actions on assuming a larger security role in the Indo–Pacific have been positive and significant. Tokyo’s willingness to call out Chinese belligerence and advocate solidarity with Taiwan are commendable. Japan’s economic response to Russia’s invasion of Ukraine was rapid and forceful, portending a similarly robust reaction to Chinese action against Taiwan.

For the near term, Japan will maintain strategic ambiguity, as will the United States, on whether and to what degree it would defend Taiwan. It is not expected that Tokyo would make fundamental, formal changes in either diplomatic relations or security policies toward Taiwan. In Japanese policymaking, the prologue to effective coordination with the U.S. often lasts an exceedingly long time. The alliance must start now to convince Beijing every day that “today is not the day” to attack Taiwan.

Bruce Klingner is Senior Research Fellow for Northeast Asia in the Asian Studies Center at The Heritage Foundation.


Bruce Klingner
Bruce Klingner

Senior Research Fellow, Northeast Asia