Main Image Credit A Soryu-class submarine of the Japan Maritime Self-Defense Force. Courtesy of Wikimedia Commons/CC BY 4.0
Statements by Japanese officials regarding the vital role of Taiwan for Japan’s security suggest a long-term evolution in Japanese defence policy, which could reinforce the position of the US-led alliance in the region.
Recent statements by senior Japanese officials, such as Defence Minister Nobuo Kishi and Deputy Prime Minister Taro Aso, indicating that a Chinese invasion of Taiwan would pose an ‘existential threat’ to Japan, should come as no surprise. Indeed, the geography of Northeast Asia has historically made the political status of Taiwan a key consideration for Japanese policymakers. The statements underscore precisely why Taiwan is critical to the US’s position in Asia. Beyond its symbolic importance as a democratic entity, the geographical position of Taiwan makes its independence critical to preserving Japan’s freedom of action, and by extension the US–Japan alliance. This reality could result in Japan becoming more directly engaged with cross-strait issues.
The recent statements by Japanese officials do not represent a break from the past. Rather, they are the latest step in a gradual reorientation of Japanese policy which began in the 1990s. Although Japan’s current prime minister was quick to clarify that his administration is not committing Japan’s forces to intervening militarily in the Taiwan Strait, the structural incentives that have driven Japan’s gradual revision of its security posture could make this viable in the medium term, particularly if the ruling Liberal Democratic Party should succeed in its efforts to amend Japan’s constitution, which currently restricts the potential use of force.
Even a greater degree of uncertainty regarding a Japanese military response to a cross-strait conflict could have a deterrent effect on China. Given Japan’s status as a regional power with greater military resources than is sometimes assumed, the need to factor in potential Japanese responses could significantly complicate Chinese planning for a cross-strait invasion. In the longer term, should the country eventually shake off its self-imposed restrictions on the use of force, Japan could become a key actor in any effort to secure Taiwan. This, coupled with military and technological developments allowing Taiwan itself to play a greater role in its own defence, would make it possible for the US to play the part of an enabling power in a Taiwan scenario, intervening with forces sufficient to tip the scales in favour of local partners, rather than achieving preponderance in a contested theatre itself.
This could create long-term military and strategic opportunities for the US-led alliance by both enabling a rationalisation of the US force posture in East Asia and limiting the degree to which any conflict in the Taiwan Strait is viewed by its antagonists primarily through the lens of a superpower clash, lending both the US and China greater diplomatic flexibility. Cumulatively, this could enable US grand strategy in Northeast Asia to eventually emulate the Nixon Doctrine, which encouraged allies to take a more prominent role in order to both limit US commitments and enable greater diplomatic flexibility, escaping the strictures of framing competition with the USSR through a narrow bipolar lens. This need not entail the abandonment of US alliance commitments, but rather a greater degree of burden-sharing and a more prominent role for regional actors. Shared priorities – such as securing freedom of navigation in the South China Sea and at key chokepoints like Malacca – would remain exclusively US responsibilities, which could be better resourced if Japan eventually assumes a more prominent role in the north.
Taiwan is vital to the security of Japan by the very nature of its position. The island, which Admiral Ernst King once described as the ‘cork in the bottle’ of the South China Sea, effectively straddles the major sea lines of communication through which a large portion of Japan’s imports in sectors such as energy and food must pass. A People’s Liberation Army (PLA) Navy based out of Taiwan, which would be able to control routes of egress from the South China Sea and project its submarines beyond the first island chain, would have an effective veto over Japan’s supplies of vital resources. Taiwan is also roughly 100 km from Japan’s southernmost islands, including Yonaguni and the disputed Senkaku Islands, and is 500 km from Okinawa.
In a modern operating environment, the basing of Chinese ballistic and cruise missiles on Taiwan would multiply the threat vectors facing Japan and, given the proximity of Taiwan to islands like Okinawa, would shorten defenders’ warning times, thereby complicating Japanese efforts at integrated air and missile defence. The effect of Chinese control over Taiwan, then, would be to turn Japan’s southern flank and make its strategic position all but untenable.
It is thus unsurprising that successive Japanese administrations have gradually revised Japan’s security posture to take this reality into account. For example, in 1997 the Hashimoto administration passed a revision of the US–Japan Security guidelines to include ‘situations surrounding Japan’, which was partially a veiled reference to Taiwan. Similarly, the subsequent Keizo administration demurred on officially endorsing the Clinton administration’s ‘three noes’ policy, which contained an explicit promise not to support either Taiwan’s independence or its membership of international bodies comprised of sovereign states.
The Abe administration, which worked to free Japan of some of its post-war constitutional constraints, similarly enhanced relations with Taiwan in a number of areas. Seen in this light, the statements of senior policymakers regarding Taiwan and the Japanese government’s commissioning of studies examining military options during a Taiwan Strait crisis should come as little surprise.
These developments reflect the latest iteration in a gradual evolution of Japanese policy, driven less by the preferences of individual administrations than by immutable geographical realities. Though the prime minister was quick to deny any suggestion that Japan would become militarily involved in a Taiwan scenario, a direct Japanese role in the defence of Taiwan could represent the eventual culmination of this long-term evolution. While in the immediate term Japan will likely play the role of providing logistical support for US forces, the evolution of Japanese policy could provide a more significant medium-term strategic opportunity for the US–Japan alliance. If they were to become directly involved in stabilising the Taiwan Strait, the Japan Self-Defense Forces would arguably be better positioned to safeguard Taiwan’s freedom of action than regional US forces. Unlike rotationally deployed US forces that must be redeployed from the continental US – straining readiness cycles – the Japan Maritime Self-Defense Force (JMSDF) is regionally postured.
The Japanese fleet, with 34 destroyers and 11 frigates, is currently Northeast Asia’s largest force of permanently stationed major surface combatants (vessels of destroyer size or greater). Moreover, Japan’s large and capable fleet of Soryu-class diesel-electric submarines could arguably be better suited to denying shallow littoral waters in and around the Taiwan Strait to PLA Navy vessels than US nuclear-powered submarines, which are optimised to operate in deeper waters. Japan’s anti-submarine warfare capabilities and its Type 12 ground-based anti-ship missiles could also constrain the freedom of action of China’s surface vessels and submarines in the northern parts of the first island chain from positions astride the Tokara and Miyako Straits. Tracking these assets and planning for contingencies in which they are deployed in a cross-strait scenario would prove a daunting and resource-consuming task for the PLA.
A JMSDF which has more locally available vessels would also potentially be well-positioned to help manage other contingencies. For example, analysts have raised the question of how well-positioned the US Navy is to conduct lower-intensity operations such as convoying merchant vessels, which may be necessary in the event of a PLA Navy quarantine or blockade of Taiwan. Such a blockade might not entail direct kinetic action by China, but rather the declaration of an exclusion zone coupled with seizures of unguarded vessels.
The major challenge in such contests, which may fall below the threshold of open warfare, is to provide numbers of hulls sufficient to protect a steady stream of shipping from interdiction. As this would strain US naval posture and readiness, support from the smaller but regionally postured JMSDF could prove critical to convoying operations for vessels approaching Taiwan. A more direct role in functions such as convoying – which do not entail offensive action – might also be more politically palatable in Japan in the short to medium term.
This is not to say that the US could simply shift the burden of defending Taiwan onto Japan, even if Japan assumes a direct military role. Air operations over the island would almost certainly need to involve the US. Moreover, China may well seek to deter Japanese involvement or divert the attention of Japanese forces in a Taiwan crisis by, for example, simultaneously menacing the Senkaku Islands; indeed, China has linked the two issues in the past.
This would seem to necessitate a role for the US Marine Corps and its expeditionary advanced base operations concept, which is geared towards operating from offshore islands, denying them and their surrounding sea space to an opponent. Finally, the possibility that China may threaten nuclear first use against Japan would make US extended deterrence vital to providing Japanese decision-makers with freedom of action.
However, a steady evolution in Japanese policy towards greater involvement in a Taiwan Strait crisis, coupled with Taiwan’s own growing capacity to execute an asymmetrical air and sea denial strategy, may in the long term allow the US to adopt a different strategic approach in Northeast Asia.
This would mirror the Nixon administration’s Guam Doctrine, which aimed – where possible – to leverage the resources of regional major powers while the US provided support and enablers in key areas. The US could in the long term shift its posture in Northeast Asia towards enabling both Taiwanese and Japanese forces, rather than being enabled by them. This would shift US priorities from achieving contested theatre entry to roll back aggression in the Taiwan Strait – an increasingly unlikely objective in any case – to enabling local forces to both achieve sea denial in wartime and thwart more calibrated coercive activity.
Supporting efforts by Japan to secure its southern littoral with US amphibious capabilities, enhancing Japan’s capacity for air and missile defence, and ensuring that extended nuclear deterrence to Japan precludes nuclear blackmail may have greater long-term salience than projecting power into the Taiwan Strait, as these actions would free up Japan’s own forces to take on roles for which they are better positioned.
A lighter footprint posture in the northern parts of the first island chain could free up the US’s own assets to focus on the South China Sea – the part of the region where there is no local power or coalition capable of balancing the PLA Navy’s South Sea Fleet. Moreover, the effect of reframing the role of the US in a Taiwan conflict as being part of a balance-of-power framework, as opposed to the PLA’s primary antagonist, could to some extent limit the degree to which a Taiwan crisis is viewed primarily through the lens of a bipolar superpower clash, which limits both US and Chinese diplomatic options. This would go some way towards facilitating the eventual negotiations which must follow any conflict. Given historical Chinese fears of a more assertive Japan in East Asia and the belief that the US–Japan alliance restrains this development, the prospect that China’s behaviour in the Taiwan Strait is catalysing the normalisation of Japan’s military posture may contribute to long-term deterrence.
To be sure, this depends on Japanese policy continuing on its trajectory towards greater involvement in the Taiwan Strait. While currently constrained by constitutional restrictions, the Japan Self-Defense Forces could become more usable in a Taiwan scenario if the current reframing of the status of Taiwan as an existential risk for Japan continues. The weight of geography makes this more likely than not, creating important opportunities for the US-led alliance in the region.
The views expressed in this Commentary are the author’s, and do not represent those of RUSI or any other institution.
Have an idea for a Commentary you’d like to write for us? Send a short pitch to firstname.lastname@example.org and we’ll get back to you if it fits into our research interests. Full guidelines for contributors can be found here.
Dr Sidharth Kaushal
Research Fellow, Sea Power