The United States and Japan Should Prepare for War with China


Last week, China toughened its language against Taiwan, warning that “independence means war.” A few days prior, the Taiwanese Defense Ministry reported 15 aircraft from the Chinese air force inside its air defense identification zone. This uptick in saber-rattling suggests the military challenge posed by China will likely continue, making it one of the Biden administration’s top priorities. Unlike the Trump administration, with its transactional approach to alliances, the Biden administration may find U.S. interests can be best served through strategic engagement with its allies, on this issue as elsewhere. In particular, part of the military challenge posed by China might be answered by turning to its longtime ally Japan and firming up one of the most intrinsic aspects of the United States-Japan alliance: warfighting.

The U.S.-Japanese relationship has deep roots. Perhaps due to the cultural strength of pacifism in Japan or the legal limits on what Japan’s Self-Defense Forces can do, however, the military aspect of the alliance has often been underemphasized in favor of broader strategic discussions about the stabilizing aspect of the alliance or economic and diplomatic cooperation. Beyond calls for greater interoperability, the specifics of the alliance’s military dimension are rarely highlighted despite the fact that the institutional relationship between their militaries and defense establishments are extremely complex, with several areas of possible improvement.

At its core, the purpose of the alliance is deterrence of aggression, which, in turn, is predicated on capabilities for effective warfighting. The alliance is, as often stated, the cornerstone of peace, security, and stability in the region. Those benefits come through a shared commitment to provide robust responses from peacetime to contingencies. But is the alliance equipped, postured, and authorized to do what will need to be done in a conflict?



Given China’s behavior, particularly over the past year, the allies could be preparing for the possibility of Chinese military action against Taiwan. Although some argue that that is unlikely anytime soon, what about a decade from now? The United States should prepare for that possibility, no matter how improbable it may be at any one moment. Should China attack Taiwan, Japan will likely find itself asked to support a U.S. operation in some capacity. China may also target U.S. forces in Japan — and possibly even Japan itself. Is the alliance ready to prosecute a wartime operation, including the defense of Japan? To answer this, the Biden administration could work with Japan to address several issues that will be crucial to a warfighting scenario.

The first is ensuring appropriate legal authority. Even if Japan limits its involvement to its own defense, to move rapidly away from peacetime to conflict, the allies need to ensure that Japan’s political timelines are in sync with U.S. operational timelines. For example, authorizing the Self-Defense Forces to exercise the use of force will require a Japanese prime minister to define a situation as one that threatens Japan’s survival. From there, discussions on possible supporting roles to U.S. operations that involve the use of force can occur. If the United States is clear about what sort of operational support it would likely request from Japan, Tokyo can prepare the necessary legal and political frameworks in peacetime to ensure their rapid approval at the outbreak of hostilities. Should other U.S. allies join, things like overflight and access in Japan might also become necessary. While Japan has been strengthening its security ties with key European partners and regional states such as Australia, working with Japan now could be critical to help ensure it has the necessary agreements to aid the free flow of these augmenting forces in wartime.

For any operation, the allies need to be on the same page, even if Japan’s role is limited to rear-area support. Toward this end, if they do not have a joint operational plan for a contingency involving Taiwan, have they at least developed and shared their own plan with each other? Additionally, the United States and Japan might ask themselves whether they are confident the existing coordination mechanisms for their parallel command and control structures will best serve their forces in what is likely to be a rapidly changing battlespace with degraded information. Finally, because operations would be executed from Japanese territory, are the allies’ current munition and fuel stocks sufficient to sustain a campaign? If the Biden administration initiates a review of all of these questions, the allies could work together to address potential discrepancies and shortfalls.

Because hostilities with China would likely mean attacks on Japan, the allies may need to ensure that their defenses and strike capabilities are robust. In addition to reviewing how they can further strengthen their air and missile defenses, particularly after Japan cancelled its planned purchase of the Aegis Ashore ballistic missile defense system, the allies might need to examine how effective their passive defenses are (i.e. hardened fuel lines or depots; hardened aircraft shelters; decoys) that enable them to remain in the fight for an extended duration. If the Aegis Ashore defensive system proved too difficult for Japan to field, it is safe to assume that it will be even harder for it to field its own offensive ground-based intermediate-range missiles anytime soon. As such, the allies could discuss Japan’s willingness to host U.S. systems on existing bases. Or, assuming even that may be difficult, at the very least they could prepare and exercise for the United States to rapidly deploy such systems to Japan during a conflict. Even in the absence of these systems, because the allies have advanced sea-based and air-based missiles, they could review their data-sharing capabilities and reexamine their joint targeting cycles in light of China’s rapid military modernization and reorganization in recent years. In any war that will likely involve cyber, space, and electromagnetic domains, the allies may also need to make sure their networks, sensors, and platforms are hardened to thwart Chinese attacks targeting their command, control, communications, computers, intelligence, surveillance, and reconnaissance nodes. All of these efforts will take time.

Given the likely involvement of Japanese civilians if Japanese islands are attacked, Japan may also need to prepare for a whole-of-government response. Casualties would occur, potentially even mass casualties in Japanese population centers. Are the allies prepared to conduct what would become history’s largest non-combatant evacuation operation? This is not a question of having enough ships and planes. Rather, it is whether the allies have the right legal authorities and capabilities to protect ports of embarkation and disembarkation and to distribute food and supplies to potentially tens of thousands of civilians. And if the allies begin to lose assets and personnel, they could be called upon to perform combat search and rescue operations across the East China Sea and to assist civilian medical staff in Japan. Some of these issues involve pre-positioning, while others involve legal questions such as whether U.S. military personnel can rapidly assist civilian medical staff in municipal hospitals simply by a request from the Japanese government. All involve disparate parts of the two governments. Coordinating expected responses in peacetime could help prepare for what is likely to be a chaotic situation.

Finally, the allies need to discuss what force posture best serves them. For example, in a recent RAND Corporation report in which I examined Japan’s potential contributions in an East China Sea contingency, I found the farther west from Okinawa a conflict takes place, the greater the challenges Japan would face in areas such as airlift, sealift and logistical support. Understanding these challenges, the allies could benefit from examining whether their current laydown of forces is adequate. If Japan is facing challenges in some areas, the allies could discuss necessary adjustments to how U.S. capabilities are postured at their current locations. In recent years, the Self-Defense Forces have opened several bases in Japan’s southwest island chain. Is there utility, for example, in having U.S. and Japanese forces co-located at these bases? And with the increase in Japan’s F-35 fleet, continued efforts to build up amphibious capabilities, and plans to field a future fighter and unmanned platforms, what additional changes to U.S. forces can be made to augment the combined capabilities?

No one expects the Biden administration to address all these issues quickly. Although the allies are currently focused on negotiating Japan’s  host nation support, a more critical issue is whether the allies have the capabilities to fight in a regional contingency, even near outlying Japanese islands. Looking ahead — rather than focusing solely on broad strategic initiatives, as the allies are prone to do — efforts could be made to bolster the warfighting aspect of the alliance to prepare it to fight and win if hostilities erupt. The longer these efforts are put off, the steeper the challenges could become for future administrations.



Jeffrey W. Hornung is a political scientist at the nonprofit, nonpartisan RAND Corporation. 

Image: Mass Communication Specialist 2nd Class Natalie M. Byers