Japan confronts an increasingly difficult security environment. Despite the current media attention on North Korea, a very real but largely one-dimensional nuclear threat, Japanese strategists are concerned primarily with the broader and more multidimensional challenge posed by the rise of China and its territorial ambitions in the East China Sea. Japanese Prime Minister Shinzo Abe has been more forward-looking regarding security affairs than his predecessors. He has moved to strengthen Japan’s defense capabilities, reorganize its security policymaking institutions, and increase its military budget after a long period of decline, while loosening some restrictions on its military forces and enhancing Japan’s intelligence capacity. These measures, however, can only marginally slow a shifting balance of power. A rethink of military strategy, one that looks to buttress deterrence even in the absence of military dominance, is urgently required. 

Japan’s current approach might be labeled a strategy of “forward defense” and is centered on defeating aggression as quickly as possible at the outer limits of Japanese territory. To execute that strategy, it has built traditional maneuver forces designed to fight decisive battles. Although forward defense was entirely reasonable during the early post–Cold War period, it is a poor fit for an evolving environment in which China would enjoy significant advantages at the outset of a conflict. To mitigate its vulnerability, harness the full potential of its alliance with the United States, and increase its ability to deter China, Japan should shift instead toward a strategy of “active denial”—one focused not on fighting pitched battles at the outset but on maintaining a force that can survive an initial assault and continue to harass and resist enemy forces, thereby denying them quick, decisive victories and driving up the risks and costs of military aggression. 

Evolving Balance of Military Power

Over the past 20 years, China’s military modernization has increased the magnitude and nature of Beijing’s strategic challenge to Tokyo. China’s military budget has grown in step with the country’s economic expansion, increasing by an inflation-adjusted 665 percent from 1996 to 2017 and now totaling some $153 billion. Japan’s defense budget, in contrast, grew by only 22 percent during the same period. At $47 billion, it is now less than one-third the size of China’s.

The development of China’s “anti-access/area-denial” (A2/AD) capabilities, designed to impede the flow of U.S. forces into the region and limit their operational freedom once in the theater, poses particular challenges. These capabilities include roughly 40 modern submarines, antisatellite systems, and, most important, a large and sophisticated arsenal of conventionally armed missiles. Of China’s roughly 1,300 conventionally armed ballistic missiles, some 150 to 500 have the range to strike targets in Japan, as do hundreds of its ground- and air-launched cruise missiles. These highly accurate missile systems could destroy key nodes in Japan’s defense infrastructure, including air bases, air defenses, communications hubs, and military ports, crippling Tokyo’s ability to resist follow-on attacks by Chinese air and/or naval forces.  

More recently, China has also developed a formidable array of maneuver forces. It has doubled its modern fighter aircraft inventory over the last seven years, and its air forces now outnumber the combined total of Japanese and local U.S. air forces (including U.S. aircraft forward-deployed to Japan and Guam) by a margin of two to one. Given current build rates, China’s advantage in modern fighter aircraft is likely to rise to three to one by 2025. China has greatly accelerated destroyer production, and by 2025 it will operate as many destroyers as the United States and Japan do in the western Pacific—and far more frigates. The Chinese People’s Liberation Army (PLA) is also moving rapidly to address its remaining weaknesses in areas such as antisubmarine warfare, replenishment of ships at sea, and cargo and tanker aircraft. 

The overall quality of Chinese systems and training is not up to U.S. standards, though China has narrowed the gap across the board. In the event of an attack on any of Japan’s four main islands, Japanese and U.S. forces would enjoy inherent defensive advantages and could almost certainly repel a Chinese assault. However, in the context of Beijing’s aspirations for greater control in the East China and South China Seas, Tokyo has cause for concern about the security of its offshore islands, where China is in a position to mount a serious military challenge. While a deliberate Chinese attack or invasion of these islands is unlikely, a clash there could escalate quickly.  

Japan’s Ryukyu Islands chain stretches some 600 miles from Japan’s southern island of Kyushu, and the disputed Senkaku Islands (known in China as the Diaoyu Islands), as well as the Yaeyama Islands group at the end of the Ryukyu chain, are twice as far from Kyushu as they are from China’s continental bases. There are some 29 PLA air force and naval air bases within fighter range of the Senkaku Islands but only four U.S. and Japanese bases within the same distance.U.S. and Japanese tankers could support aircraft flying from more distant bases, but only at reduced sortie rates and with greater stress on pilots and aircraft. The comparative scarcity of nearby Japanese and U.S. military infrastructure and the proximity to mainland bases magnify the threat of a Chinese combined air and missile attack, possibly supported by submarines and surface ships. 

Problem of Military Strategy

To understand how Japan should begin to rethink its military strategy, it is useful to consider that strategy in the context of three ideal-type approaches to conventional defense and deterrence: forward defense, denial, and punishment. Forward defense looks to defeat an attacker’s military forces as quickly and as far forward as possible, preferably at or near the state’s frontiers. Denial strategies seek to prevent conquest through prolonged, active resistance, often by yielding at least some ground and avoiding a decisive battle until the balance of forces has shifted in the defender’s favor. Punishment hinges on the ability to inflict unacceptable losses on an attacker’s valued assets—for instance, by destroying targets in its home country.

During the early Cold War, Japan practiced a “shield and spear” denial strategy. Japanese forces (the “shield”) would delay and harass an invader until U.S. forces (the “spear”) could arrive. In the 1970s, however, Japan’s military emphasis began to shift toward forward defense. By the end of the Cold War it had one of the world’s largest defense budgets, largely allocated to the maintenance of traditional maneuver forces (such as large warships and large formations of aircraft operating from full-service air bases) that could engage any potential aggressor in a direct military confrontation. Despite the adoption of a “dynamic defense concept” in 2010, Japan continues to maintain its focus on forward defense. Indeed, by building an expensive amphibious assault capability for an immediate counterattack on potential adversary lodgments on Japan’s outer islands, it has effectively doubled down on that forward defense strategy.

This strategy made sense in the context of the late Cold War and early post–Cold War periods, when Japan could meet any potential aggressor on equal or better terms. With the rise of China, however, this assumption no longer holds. China’s long-range precision-strike capability poses a lethal threat to Japan’s military infrastructure and, to a lesser extent,its large military formations. Undertaking early counteroffensive action in the Senkaku Islands or southern Ryukyu chain would risk catastrophic defeat and potentially destroy Tokyo’s will or ability to continue the fight. Missile defenses cannot provide a reliable or airtight solution, especially given their high costs. 

A Better Alternative

A better option for Japan is an active denial strategy, focused on demonstrating to Chinese leaders that any attack would likely turn into a protracted conflict, one in which U.S. and Japanese forces would enjoy clear advantages. The priority in a denial strategy would be not a quick victory but rather denying China early and decisive success, allowing Japanese forces to effectively resist until U.S. reinforcements could arrive. In contrast to Japan’s early Cold War denial strategy, which was built around relatively immobile and regionally organized ground forces, active denial would be dynamic and mobile and would include tactical offensive capability. 

The active denial strategy has two mutually reinforcing elements: a resilient force posture and a reordering of mission priorities. The first element, a resilient force posture, refers to the ability of Japan’s military to absorb attacks and continue to operate effectively. Resilience will require an expanded and strengthened system of military infrastructure, even if such investments leave somewhat less money available for weaponry. Civilian airports, for example, could be prepared to support air force operations, enabling the quick dispersion of Japanese and U.S. aircraft, greatly increasing the number of targets an attacker would need to strike, and reducing Japan’s vulnerability to missile attacks. Expanding the number of ports and naval supply locations would similarly boost the survivability and flexibility of the Japanese fleet. 

Mobility and deception can also play an important part in developing resilience. Japan could employ new mobility concepts similar to those currently being tested by the U.S. military to complicate an adversary’s targeting problem. These include “agile combat employment,” the temporary dispatch of small numbers of combat aircraft (usually two to four fighters) supported by a single cargo aircraft with fuel and munitions to austere air bases. Other sorts of mobility enhancements, such as the development of a civilian reserve fleet of fast transport ships and the naval reservists to staff them, are central to maintaining coherent defenses in the Ryukyu Islands, where the ability to reinforce positions and replace destroyed systems and expended munitions will be critical. 

Active defenses against air and missile attacks are also important but should be considered in the context of the larger resiliency effort. Missile defenses, in particular, loom large in the public imagination, since they can, at least in theory, protect civilian targets. But they also absorb inordinate amounts of the defense budget, despite the fact that concealment, dispersion, and mobility are often more economical and effective strategies. Luring China to fire missiles at empty shelters or low-value targets would have the same effect as shooting down those missiles in flight or penetrating Chinese airspace to destroy them prior to launch, but the former may be achieved more cheaply. 

The second element of the active denial strategy flows from the first. In keeping with the objective of resilience, Japan should establish a clear hierarchy of mission priorities: first, defending key assets that enable the government and military to continue functioning; second, isolating and striking adversary forces that land on Japanese territory; and third, counterattacking to retake lost territory after U.S. reinforcements arrive. 

Business as usual in U.S.-Japanese military cooperation and Japan’s own defense effort is a losing proposition.

The most immediate and important mission, the defense of key military and civilian assets, is associated with integrated air and missile defense (IAMD), antisubmarine warfare, and defensive antisurface warfare tasks. Modernizing older aircraft and acquiring additional 4.5-generation fighters, such as the F/A-18E/F or F-15SE, would allow the small number of F-35As to serve as more effective force multipliers for the air effort. Acquiring some number of F-35Bs, capable of operating from short runways or amphibious assault ships, would also enhance Japan’s ability to sustain an air battle while under attack in the Ryukyu Islands. In the maritime domain, supplementing its fleet with smaller and cheaper multifunction frigates would help to improve Japan’s ability to survive an initial Chinese attack in the southwestern islands. 

Focusing on these tasks would require a reversal of Japan’s current budgetary priorities, which allocate 50 percent more money to the army than to either the air force or the navy. It will also require improving coordination and introducing joint commands so that the different services can function more effectively as an integrated whole.  

A New Defense Strategy 

Business as usual in U.S.-Japanese military cooperation and Japan’s own defense effort is a losing proposition. The alliance between the United States and Japan continues to serve both parties’ critical interests—among other things, it anchors the U.S. position in Asia—but it is entirely reasonable for the United States to push for Japan to increase its military spending and continue defense reform. At the same time, however, spending alone will not be sufficient to meet the evolving threat posed by China. A fundamental rethink of strategy will be critical. 

With Chinese incursions into the Senkaku Islands on the rise, Japan would do well to adopt an active denial strategy that demonstrates its capacity for a viable, long-term defense of the islands. By denying an adversary the possibility of an early knockout blow and promising to turn any conflict into a protracted affair, the strategy would significantly buttress deterrence at a time when achieving dominance in areas close to China at a reasonable price is fast becoming unrealistic. 

Equally important, a denial strategy would increase crisis stability and mitigate first-mover advantages. Japanese and forward-deployed U.S. forces would not be optimized for immediate offensive action, diminishing Chinese leaders’ fear of attack during a crisis and reducing their incentives for striking first. Similarly, Japanese and U.S. forces would be less vulnerable to a first strike and, therefore, also have less incentive to launch a preemptive attack. While all three governments should seek ways to ease political tensions, military factors will also influence outcomes. An active denial strategy has unique potential to improve deterrent capability while mitigating crisis instability. 

CORRECTION APPENDED (July 16, 2018)An earlier version of this article referred to a hypothetical attack on any of China's four main islands. The reference was meant to be to any of Japan's four main islands. We regret the error. 

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