Ryukyu Chain in China’s Island Strategy

Publication: China Brief Volume: 10 Issue: 18

Ryukyu Islands

In late August the Japanese daily Yomiuri Shimbun reported that the Japan Self-Defense Forces (JSDF) intend to stage their first-ever island defense exercises in December. The maneuvers will be held in concert with U.S. Navy forces to refine plans for recapturing the lightly protected Ryukyu Islands from a hostile—presumably Chinese—invading force (Yomiuri Shimbun, August 20). To date, the response from China has been rather muted considering the stakes it faces (Asia Times, August 31). As the first installment in this series on Japanese maritime strategy demonstrated, China’s People’s Liberation Army Navy (PLAN) has been making efforts to break out of the first island chain and operate freely in the Western Pacific, either to threaten the east coast of Taiwan or for some other purpose. Occupying one or more of the Ryukyus offers one way for the People’s Liberation Army (PLA) to do so. Once ensconced within the island chain, PLA forces could drive off allied navies, keeping Tokyo and Washington from slamming the nautical gateway shut.

After decades of declining to dispute Chinese access to the Pacific, Tokyo has started taking the prospect of Sino-Japanese maritime competition more seriously, and it grasps the geographic dimension of any such contest. Indeed, the editors of Asahi Shimbun recently fretted that Prime Minister Naoto Kan’s Advisory Council on Security and Defense Capabilities had issued a report that espoused modifying the government’s National Defense Program Guidelines. The Guidelines shape JSDF strategy and forces and thus constitute an indicator of how the government views the security setting. The editors interpreted the Advisory Council report as embracing “the logic of force.” For them it marks a dangerous step back from Japan’s pacifist traditions (Asahi Shimbun, August 28).

That there is an antagonistic element to Sino-Japanese relations, then, is far from obvious to many Japanese, who quarrel among themselves over the nature of China’s rise and its security implications for their nation. Former Defense Minister Shigeru Ishiba, for example, recently told the Beijing-Tokyo Forum, “There is no need for us to keep stressing that China is a threat. The China-threat theory in Japan has turgidly stirred unease among the people” (Xinhua News Agency, August 31). Accordingly, interactions between the two Asian heavyweights defy easy prognosis. Trade and commerce are knitting their economies together even as strategic ambivalence buffets bilateral ties. Conflicting impulses and trends have given rise to what the Japanese-mainstream dubs a “politically cold and economically hot” relationship. While officialdom refrains from portraying China’s ascent as a challenge to the U.S.-led Asian order, the planned Ryukyu exercises indicate that Tokyo has quietly taken to hedging its bets.

Prospective Contingencies at Sea

The Japanese armed forces must contend with a variety of contingencies involving the Ryukyus. One possibility is a narrowly focused Chinese attack designed to open a corridor through the archipelago. PLA forces might capture islands adjoining one or two straits through the archipelago. A prime candidate is Miyako Island, which abuts both the Miyako and Ishigaki straits, the passages of choice for PLAN flotillas in recent years judging by their deployment patterns [1]. Missile-armed troops emplaced on Miyako could safeguard PLAN shipping through each strait, letting the island perform double duty.
Just to the south, Ishigaki Island offers another attractive target. Chinese skippers might favor Miyako Strait from a navigational standpoint. It is deeper and broader than the Ishigaki Strait, offering more maneuvering room and more scope for submerged transit. Yet vessels essaying the northern route must cross under the shadow of Okinawa, within range of allied weaponry. Consequently, the Ishigaki Strait could become the PLAN’s preferred exit from the near seas. And indeed, the much-discussed intrusion of a Chinese Han-class nuclear attack submarine in 2004 took place in this southern passage [2]. Occupying both islands would grant the PLA full control of the southern passage and partial control of the northern one, holding open both options and diversifying the Chinese operational portfolio. Some signs suggest that the JSDF is starting to take this prospect seriously. The military is considering stationing small contingents on the two islands (Japan Today, July 20).

Alternatively, the PLA might wrest the entire Ryukyu chain from Japan, opening up the full range of possibilities. Either way, an island campaign would further several purposes. It would promote what the Pentagon terms “anti-access/area denial” (A2/AD) operations, meaning efforts to bar maritime Asia to U.S. reinforcements while keeping forces already in the theater from entering such areas as the Taiwan Strait. Operating between the island chains, PLAN submarines and surface action groups would mount a defense-in-depth against U.S. Navy expeditionary groups steaming west from bases like Guam, Pearl Harbor, or San Diego. Missile and torpedo attacks would inflict serious damage while depleting fuel, ammunition, and other stores these forces need to wage war after reaching the combat theater.

While few Chinese mariners would admit to the precedent for ideological reasons, the PLA in effect intends to reprise Imperial Japanese Navy strategy for World War II. During that time, Japanese naval planners envisioned depleting westward-bound U.S. task forces through aerial and subsurface raids conducted from well-supplied island strongholds. Attrition would even the force ratio, softening up the U.S. fleet as a precursor to the decisive battle. Imperial Japanese forces, however, enjoyed ample time beforehand to fortify the islands and atolls against attack. Allied forces would doubtless raid Chinese positions, denying PLA invaders time to dig in. How such encounters would play out is anyone’s guess.

There appears to be a “north-south” as well as an “east-west” axis to China’s island strategy. By controlling Japan’s southern flank, PLA forces entrenched along the island chain could supply air and sea cover for PLAN vessels cruising off the east coast of Taiwan. For example, stealthy, missile-armed Type 022 Houbei-class catamarans stationed at the many small harbors in the Ryukyus could hold off allied forces while the PLAN fleet overcame the Taiwan Navy and pounded away at shore targets. In fact, the PLAN flexed this capability during live-fire exercises in the East China Sea this past July [3]. Moreover, small craft and mobile missiles operating from the islands and the Chinese coast could impede north-south movement, foreclosing a juncture between allied forces based in Japan and any reinforcements en route from South or Southeast Asia.

Nor are the benefits of island operations solely military in nature for China. For instance, Beijing might seize the disputed Senkaku/Diaoyutai Islands as a political-psychological gambit. China and Japan both claim the two uninhabited islets and adjacent waters (as does Taiwan), along with sizable deposits of undersea oil and natural gas. The two nations last sparred over the islands in early 2005, setting loose vitriolic anti-Japanese protests on the mainland. As Peter Dutton notes, Beijing has deftly stoked “managed confrontation” with Tokyo in the East China Sea, using Japan’s dark imperial past to inflame anti-Japanese sentiments when it suits China’s political needs [4]. Chinese leaders might give managed confrontation a more forceful twist in some future Sino-Japanese encounter. Small wonder Beijing pays the islands such close attention, considering the operational, strategic and diplomatic windfalls occupying them could yield.

How Should Tokyo Answer Beijing’s Challenge?

Despite this grim-sounding forecast, it is by no means foreordained that the PLAN can snatch the islands from Japan, much less hold them against allied counterattack. The rudimentary state of the PLAN amphibious fleet (See “PLA Amphibious Capabilities: Structured for Deterrence,” China Brief, August 19), the PLA’s lack of expeditionary experience, and other shortfalls illuminate distinct Japanese advantages in a Sino-Japanese competition. Tokyo holds a permanent geographic advantage that it can exploit by beefing up its defenses along the Ryukyu chain. And it retains military capabilities honed to a fine edge during the Cold War, most notably antisubmarine warfare (ASW). This represents solid groundwork for competitive strategy vis-à-vis Beijing.

Think back: Despite the Japan Maritime Self-Defense Force’s (JMSDF) modest combat power relative to the Soviet Navy, Japanese mariners put geographic features to good use while maximizing their operational advantages. U.S. submariners famously insist that the best ASW implement is another submarine. Modern diesel-electric JMSDF submarines guided by sophisticated sensors and tactics lent invaluable support to the offensive-minded U.S. maritime strategy of the late Cold War. JMSDF boats offset their short range and endurance compared to nuclear-powered vessels by “sitting on the bottom and waiting” for approaching Soviet submarines. Such tactics conserved fuel, reduced machinery and flow noise, enhanced concealment, and thereby boosted JMSDF boats’ chances of passive sonar detection [5].

By obstructing chokepoints with submarines, fixed- and rotary-wing ASW aircraft, and an elaborate undersea sensor network, JMSDF tacticians in effect dared Soviet skippers to risk passage through the narrow seas bordering the Sea of Japan. Most chose to remain within the first island chain. At the same time, Japanese nautical gatekeepers kept open the maritime thoroughfares to permit offensive U.S. operations against the Soviet Navy’s Far Eastern “bastions,” or enclosed seas. For Japan this division of labor paid strategic dividends beyond strictly operational and warfighting matters. Tokyo could exert pressure on Moscow without incurring prohibitive financial costs or assuming an offensive naval posture that violated the spirit of the postwar “peace constitution.” A variant of Tokyo’s Cold War strategy may suit its needs in the Ryukyus today. Reports that the JMSDF will expand its submarine fleet from 18 to 20 boats—the first such increase since 1976, at the height of the Soviet naval challenge—suggest that the Japanese leadership has decided to do just that. Chinese observers have taken notice (China Daily, August 12).

While offensive submarine warfare holds significant promise for the JMSDF, however, the fleet’s supremacy in ASW is on the wane. The PLAN submarine fleet represents the vanguard of Chinese military modernization, steadily growing more numerous, more stealthy and more lethal. In part this is simple physics. As new technology quiets Chinese boats, they are harder to find, track and kill. ASW becomes increasingly resource- and asset-intensive. Indeed, American submariners now question their own capacity for ASW in the Pacific. In short, the burden of undersea combat falls disproportionately on the defender. Whether Japan can sustain sea- and airborne ASW forces sufficient to bottle up a materially superior China is doubtful. This will be especially true should the PLA perfect its antiship ballistic missile (ASBM) – a weapon ideal for striking at JMSDF “helicopter destroyers,” or DDHs, the light aircraft carriers that form the core of the surface fleet’s ASW capability.

A more offensive mindset, then, may represent the future of Japanese maritime strategy. Numbers of platforms matter, but this is not as big an obstacle as it seems. Standard JMSDF practice is to retire submarines at around 15 years of service life, assuring the fleet remains on the technological cutting edge. By contrast, U.S. Navy attack submarines serve for around thirty years. Judging by the American example, Tokyo can enlarge its submarine fleet with minimal effort and expense. It can simply build new boats at the current rate while leaving older ones in service longer.

A similar shift from defense to offense could take place in the realm of mine warfare. The JMSDF excels at mine countermeasures (witness its mine-clearance operations after the first Gulf War) but places little emphasis on offensive minelaying. Fielding such a capability should nonetheless prove rather simple for tech-savvy Japan. Even primitive sea mines have stymied modern navies in recent years—again, with Iraqi minelaying off Kuwait in 1990-1991 offering a prime example. In short, combining existing assets with new, cheap ones could let Tokyo cordon off its arc of the first island chain, imposing prohibitive costs on the PLA should it choose to force its way out of the China seas.

Finally, an obvious step for the JSDF would be to fortify the islands themselves against attack, sparing Japanese forces the hazards of retaking them from PLA occupiers. As noted before, the islands are virtually undefended. Dug-in and armed with antiship and antiair weaponry, Japanese troops could make the Ryukyus exceptionally hard targets for PLA forces operating far from their bases. Effective joint and allied operations could keep the PLA from storming the islands or, failing that, cut them off, isolate them and wait them out in wartime. Either way, Japan would come out ahead in the Sino-Japanese competition.

How Japan will fare at this is less clear. To glimpse the future of Sino-Japanese maritime competition, it is worth asking what military missions the JSDF must perform to exploit Asia’s intricate maritime geography, how well-configured and—trained Japanese forces are to prosecute such missions, and what gaps in strategy, doctrine, and force structure the JSDF must plug to compete successfully with Beijing.

Will Japan act on its advantages? It is hard to say. In the final analysis, the obstacles before Tokyo are more intellectual and emotional than military in nature. Japanese politics and postwar traditions will work against greater vigor at sea, while military institutions like the JSDF habitually prefer doing more of the same. If these reinforcing tendencies win out, Tokyo will continue attempting to match the PLA ship-for-ship while depending on Washington to tip the military balance. Both the upcoming island defense exercises and Ground Self-Defense Force plans to organize an amphibious force to retake islands wrung from Japan tacitly admit that Tokyo does not expect to hold them against an initial PLA assault. JSDF forces will have to fight at a disadvantage to recover lost territories (Asahi Shimbun, September 1).

Advantage: China.


1. Yu Kaijin, Li Guansuo, and Zao Yongheng, “Island Chain Analysis,” Ship and Boat 5 (October 2006): 14.
2. Peter A. Dutton, Scouting, Signaling, and Gatekeeping: Chinese Naval Operations in Japanese Waters and the International Law Implications, U.S. Naval War College China Maritime Studies no. 2 (Newport: Naval War College Press, February 2009): 4-17.
3. Andrew S. Erickson, “Chinese Anti-Ship Cruise Missile Firing as Part of Combined Arms Anti-Carrier Exercises in East China Sea, 30 June-5 July,”
4. Peter A. Dutton, Testimony before the U.S.-China Economic and Security Review Commission, February 27, 2008,
5. Alessio Patalano, “Shielding the ‘Hot Gates’: Submarine Warfare and Japanese Naval Strategy in the Cold War and Beyond (1976-2006),” Journal of Strategic Studies 31, no. 6 (December 2008): 870.