The Ryukyu Chain: Japan's Southern Islands and the Geography of Taiwan's Defense
Stretching from Kyushu southwestward toward Taiwan, the Ryukyu island chain forms a natural barrier between the East China Sea and the Philippine Sea. The chain includes Okinawa — site of the largest American military concentration in the western Pacific — and continues through progressively smaller islands to the Yaeyama group, whose southernmost point lies less than 75 miles from Taiwan’s northeastern tip. This geography is not coincidental to the Taiwan question. It is central to it. Any Chinese military operation in the Taiwan Strait must account for the Ryukyu chain, and any American or Japanese response to such an operation would use the chain as its primary operating framework.
Japan has spent the past five years accelerating the militarization of its southwestern island chain in ways that represent a fundamental shift from its post-war defense posture. The Japan Ground Self-Defense Force has established missile units on multiple islands in the chain, positioning Type 12 surface-to-ship missiles and surface-to-air missile systems on Miyako-jima, Ishigaki, and other islands southwest of Okinawa. These positions can engage surface targets in the strait approaches and threaten the sea lanes that PLA naval forces would use to approach Taiwan from the east. The positioning is deliberate, coordinated with American operational planning, and represents a Japanese strategic commitment to the Taiwan contingency that would have been politically impossible to articulate publicly as recently as 2018.
Okinawa hosts approximately 26,000 American military personnel across installations that include Kadena Air Base, Camp Foster, and several other facilities. Kadena’s F-15 and F-35 aircraft provide air defense and offensive strike capability that would be central to any American air campaign in the Taiwan contingency. The base’s geographic position — roughly equidistant from Taiwan and the Chinese mainland — makes it both highly valuable and highly vulnerable. PLA ballistic missiles can reach Kadena with approximately ten minutes warning time. American planners have invested in hardening, dispersal, and the ability to sustain operations from a damaged or partially degraded Kadena, but the base cannot be made invulnerable to a sustained missile campaign by a force with the inventory the PLA Rocket Force possesses.
The Senkaku Islands — administered by Japan, claimed by China, and called the Diaoyu Islands in Chinese — sit at the northern end of the Ryukyu chain and represent an overlapping territorial dispute that could serve as either a tripwire or a complication in a Taiwan contingency. Chinese coast guard and maritime militia vessels have operated in the waters around the Senkakus with increasing frequency and assertiveness over the past decade. A Taiwan crisis that simultaneously involved Chinese action around the Senkakus — whether as a deliberate escalation, a coordinated operation to split Japanese attention, or an opportunistic move under the cover of the larger conflict — would create political and military complications for Japan that its defense planners must account for.
Japan’s revised National Security Strategy, published in December 2022, explicitly named China as an unprecedented strategic challenge and authorized for the first time the acquisition of counterstrike capabilities — the ability to strike targets on the territory of an adversary. The decision was historically significant: Japan’s post-war constitutional interpretation had restricted its self-defense forces to purely defensive operations and excluded offensive strike from the permissible mission set. The counterstrike capability acquisition changes the military calculus for Chinese planners who must now account for Japanese long-range precision strike in their operational modeling of a Taiwan contingency.
The question of whether Japan would exercise that capability in a Taiwan contingency remains politically contested domestically. Japanese public opinion on involvement in a Taiwan conflict is ambivalent. The legal framework authorizing counterstrike is new and untested. The political leadership’s willingness to commit to the use of the capability depends on how the scenario develops — whether Taiwan is perceived as fighting for survival, whether American forces are engaged and taking casualties, whether Chinese operations directly threaten Japanese territory or Japanese citizens. The answers to these questions during a real crisis cannot be predicted from peacetime polling.
What can be stated with confidence is that the Ryukyu chain has never been more militarily relevant to Taiwan’s security than it is today, and that Japan has made more explicit commitments to that relevance than at any point in its post-war history. The geography was always there. The political will to use it is being built.