Taiwan’s Evolving Response to China’s Grey Zone Actions

‘Grey zone’ as a qualifier for challenges, threats and even warfare describes an approach that seeks results from action below the threshold of war or armed conflict. Attempts to frame a precise definition raise theoretical and practical questions. Can action ‘below the threshold’ of war be a form of ‘warfare’, or is the threshold subjective and open to manipulation? Can grey zone action be deterred without threatening to cross the line into a state of war? How can the victim of aggression escape a trap where moves to deter grey zone challenges attract condemnation for ‘provocation’ or ‘escalation’ that might be more damaging than the original attack?

China’s ‘campaign against Taiwan’, which Sir Alex Younger, former Chief of the UK Secret Intelligence Service, described as ‘a textbook on subversion, cyber and political harassment’, presents a compelling case study for understanding the grey zone phenomenon. While Taiwan’s situation is distinctive in some ways, the grey zone pressures it faces – including incidents such as sabotage of undersea infrastructure, election interference and digitalised disinformation – closely parallel those faced by other countries in Europe and Asia.

An understanding of Taiwan’s evolving response to the grey zone is instructive for policymakers experiencing similar challenges. The purpose of this policy brief is to draw insights from Taiwan’s experience, leading to policy recommendations that could have wider application. The brief traces the emergence and defining features of the ‘grey zone’ concept, then looks at China’s actions and Taiwan’s responses, and concludes with recommendations.

This brief is based on desk research and interviews in Taiwan between November 2024 and February 2025, including a two-day workshop involving experts and officials from Taiwan and other countries facing similar challenges (Australia, Canada, Finland, Indonesia, Japan, Latvia, Philippines, Republic of Korea, Singapore, Sweden, the UK and Vietnam).

The US Quadrennial Defense Review of 2010 noted 'The future strategic landscape will increasingly feature challenges in the ambiguous gray area that is neither fully war nor fully peace'. The actual term ‘gray zone challenges’ appeared in a paper by Philip Kapusta published in 2015, which described ‘competitive interactions among and within state and non-state actors that fall between the traditional war and peace duality … characterized by ambiguity about the nature of the conflict, opacity of the parties involved, or uncertainty about the relevant policy and legal frameworks’ (author’s emphasis). Kapusta adds that participants can ‘interpret the conflict differently’, and parties can use the resulting ambiguity about the nature of the conflict ‘to avoid accountability for their actions’. Alongside ambiguity, a more recent RAND study identified the following characteristics of grey zone activity: ‘unfolds gradually, is not attributable, uses legal and political justifications, threatens only secondary national interests, has state sponsorship, uses mostly nonmilitary tools, and exploits weaknesses and vulnerabilities in targeted countries and societies’.

The term ‘grey zone’ has become part of Western policy vocabulary, yet the critical issue of the ‘threshold’ remains contentious. Contrary to NATO doctrine that suggests there is ‘no defined threshold that separates confrontation from armed conflict because many actors intentionally try to obscure or confuse exactly where this threshold lies’, the International Committee of the Red Cross warns that ‘political narratives surrounding “competition”, “hybrid warfare”, “proxy warfare” or other “grey zone” terminology must not obfuscate the legal classification of armed conflicts and the application of IHL [international humanitarian law]’. The ICRC goes on to say that even when it is difficult to obtain clear information about the situation this should not be an ‘excuse for – or be confused with – failure to apply the law to these facts … activities such as imposition of economic measures, information operations, and espionage, by themselves, do not trigger the application of IHL’. As John Raine has argued, ‘much, but not all, of what we see being conducted in this space could be characterised as features of the difficult, new peace as much as the new warfare’.

The US Intelligence Council assesses that ‘gray zone activities and campaigns are likely to increase in the coming years and become a dominant feature of great power competition and international relations more broadly because of eroding or nonexistent norms; emerging, evolving, and expanding domains; and perceptions of their comparative advantages’. Technological developments also expand the scope for grey zone action. The internet and social media function as vectors for attack and subversion not imagined in the era when the law on armed conflict and the UN charter were written. Globalisation has also intensified the range and value of international connections, expanding dependencies that can be held hostage. As Sir Alex Younger put it, ‘propaganda, subversion and sabotage have been a feature of inter-state conflict for ever. But I think it is also fair to say that our attack surface has increased’.

Use of the grey zone to avoid accountability or attribution provides leverage in the cognitive and informational (for example, narrative) dimensions of conflict. The first battle for legitimacy is won by shifting the charge of ‘aggressor’ onto the victim, who – reluctant to be accused of ‘escalation’ – will be tempted to do nothing, even at the risk of appearing incompetent. Democracies dependent on alliances are especially vulnerable to this trap. Citizens demand accountability, and an elected leader who takes firm measures can face opposition charges of recklessness. Appear too willing to ‘escalate’ and you may trigger in your allies the fear of entrapment and end up abandoned.  

China’s Approach

The Chinese Communist Party (CCP) views bringing Taiwan under its control as a ‘historic mission and an unshakable commitment’. The fact that Beijing has not given any deadlines or outlined any proscribed methods suggests it is planning to choose a moment and a set of circumstances where ‘reunification’ can be achieved at a cost that does not jeopardise its main policy objectives: building China into a ‘great modern socialist country’ and returning it to ‘centre stage’ in the world. Put another way, the CCP prefers to win Taiwan without fighting. Its exploitation of grey zone approaches is shaped by the possibility that the US position ‘against any forced, compelled, coercive change in the status of Taiwan’ could escalate into a military intervention with catastrophic costs (similar language was adopted in a joint US–Japan statement in February 2025).

Assuming China seeks to avoid a direct clash with the US, the main obstacle to its aim of extending control is the people of Taiwan’s choice to elect governments that refuse to accept what it claims as a ‘consensus’ that both sides of the Taiwan Strait ‘work together to advance national unification’. If Taiwan were to freely choose unity, the US military would no longer be a factor. If, however, the government in Taipei changed to one that accepted Beijing’s conditions, allowing resumption of ‘normal’ cross-strait relations, China could bring the full power of its diplomatic and economic instruments to bear, marginalise the ‘separatist’ tendency in Taiwanese society, fully detach Taiwan from external support, and be reassured that Taiwan was on track to unification some time down the road. Rather than thinking of the target as the island of Taiwan, and military invasion as the method, it is more apt to see the target of Beijing’s actions as a preferred political status, and Taiwanese popular opinion as the strategic ‘centre of gravity’ (Carl von Clausewitz’s metaphor for ‘the hub of all power and movement, on which everything depends’).

While China has not formally adopted the grey zone concept in its own doctrine, a related set of concepts termed the ‘Three Warfares’ (public opinion, psychological and legal warfare) was introduced by the Central Military Commission into the Peoples’ Liberation Army (PLA) Political Work Regulations in 2003. The International Institute for Strategic Studies identifies China’s legal warfare objectives with regard to Taiwan as to: ‘intimidate and coerce Taiwanese society’; ‘erode Taiwan’s territorial claims and sovereignty’; ‘isolate Taiwan diplomatically’; ‘build legal justifications to legitimate future action against Taiwan’; and ‘promote further cross-Strait integration to keep open the option for reunification without military action’.

Beijing is quite open about its intention to bypass the government in Taipei and ‘conduct extensive and in-depth consultations on cross-Strait relations and national reunification with people from all political parties, sectors, and social strata in Taiwan, and [to] work with them to … advance the process of China’s peaceful reunification’. The PLA is also an instrument of this grey zone pressure, including through:

• Air and maritime incursions across the median line of the Taiwan Strait and adjacent to 24 nautical miles off Taiwan, and over Taiwan’s air defence identification zone. 
   
• Military exercises in the waters off Taiwan, including assigning maritime paramilitary forces in joint training with the People’s Liberation Army Navy and the China Coast Guard.
   
• Flying UAVs over offshore islands and weather balloons over Taiwan. 
   
• Broadcasting ‘news’ to Taiwanese audiences.
   
• Using marine survey vessels and hydrographic survey ships as a ‘cover’ for the military to improve its battle management around Taiwan.
   
• Cyber attacks on governmental agencies.
   
• Targeting critical infrastructure, including allegedly severing underwater cables.
   

Taiwan’s ROC National Defense Report 2023, similar to a defence white paper, recognises the risk of subversion, noting that China ‘has never let up its infiltration and wedge-driving moves in the media and on the internet. Behind its military threat, [it] is exhausting every means to incite discrepancies within Taiwan and create people’s distrust against the government’. The report highlights China’s use of the following modalities ‘aim[ed] at creating a division among our society and driving wedges among our people’:

• Hacking.
• Disseminating controversial messages, propaganda and deliberate distortion.
• Wedge-driving and provocation.
• Infiltration.
• Threats and intimidation.

To return to the threat of military invasion, intensified PLA activity, such as large-scale military exercises, erodes warning times for potential operations. Taiwan’s defence officials emphasised to the author that grey zone actions need to be viewed as part of an escalation ladder that could go to full military action but could also pivot into higher-order grey zone actions such as a ‘quarantine’ or full blockade. While the US Defense Department estimates there would probably be ‘unambiguous indicators of larger hostile actions against Taiwan’, the Commander of the US Indo-Pacific Command , Admiral Samuel Paparo, said recently that Chinese ‘aggressive maneuvers around Taiwan right now are not exercises, as they call them. They are rehearsals’.

Taiwan’s Predicament

On top of the vulnerability to grey zone attack common to all democratic systems, Taiwan’s status creates additional disadvantages by obstructing collective action. A growing number of states maintain a policy aligned with Beijing’s ‘One China’ principle, that Taiwan is an ‘inalienable part’ of the People’s Republic of China. Even states such as the US and the UK, which Taiwan considers like-minded, have some form of China policy restricting diplomatic relations and defence cooperation. UN member states that are induced to sign off on the One China principle are more likely to consider Beijing’s action towards Taiwan as an internal matter, ignoring Taiwan’s invocation of the right of individual or collective self-defence. It is therefore perhaps not surprising that when Taiwanese interviewees as part of this research identified two reasons for reluctance to ‘escalate’, the first is concern that the international community (even countries friendly to Taiwan, especially the US) would not welcome an escalation and might not back Taiwan up (an assumption somewhat borne out in wargaming). 

The second reason given for reluctance to ‘escalate’ was fear of domestic turmoil within a society split by divisions on cross-Strait relations. Scholars describe how Beijing’s colonisation of Taiwan’s ‘media ecology’ going back to the period of Ma Ying-jeou’s presidency from 2008 to 2016 has created an information infrastructure favourable to advancing its strategic objectives. 

Broadly speaking, Taiwan’s response breaks down into three areas: appeals for external support; interceptions of PLA ships and aircraft; and work to develop resilience. President Lai Ching-te launched the Whole-of-Society Defense Resilience Committee in June 2024 to work on: civilian force training and utilisation; strategic material supply; energy and critical infrastructure; social welfare, medical care evacuation readiness; and information, transportation and financial network protection. 

Analysis of grey zone approaches indicates that the recipient finding the effects of such actions intolerable can react in two ways. One is to neutralise effects through measures likely to be viewed as defensive, such as enhancing resilience. The other is to counter the aggressor’s intent, through dissuasion or deterrence responses designed to stop the action either by disabling the means to carry it out (denial), or by imposing costs to a point where the aggressor concludes that it is against their interest to continue (punishment).

Targeting intent by cost imposition entails a risk of escalation. Even where risk of escalation is deemed an acceptable price for putting a stop to the harm caused by grey zone activity, it may be rejected as a course of action because of the costs that come with being identified as responsible for escalating. For reasons connected to the ‘blame shifting’ aspect of grey zone action noted above (such as uncommitted allies and divided domestic opinion), this is especially the case for Taiwan.

Taiwan’s predicament calls for a counter-grey zone playbook with response options that bring advantage to the victim. At the difficult end of the spectrum is a set of actions where the risk/return calculus results in favour of cost imposition, even at the risk of escalation. For example, make a public warning that a drone flying into territorial airspace will be shot down – if that happens, the other side will find it harder to make a charge of ‘aggression’ stick. Or procure non-lethal weapons and draw up rules of engagement to guide a more robust response. It is likely that this category of response options, which could be termed ‘dark grey’, will grow from the adoption of uncrewed systems that can engage in the contest without loss of life, thus limiting escalation to some extent.

Dark Grey

To be effective, dark grey responses require government institutions that can promptly calculate appropriate consequences and carry them out without delay, ensuring the perpetrator as well as domestic and international audiences understand the cost imposition consequent to that grey zone action. Responses should maintain the distinction between perpetrator and victim by calling out grey zone moves in public and diplomatic arenas (where possible in advance) and explain why they are unacceptable and why consequences must follow.

This is easier said than done. Difficulties arise where grey zone actions are not immediately obvious, and their effects are sometimes not detected until it is too late. A RAND analysis concluded that many low-end grey zone activities ‘cannot be deterred’, and identified eight criteria required for deterrence to work on the ‘high end’ of the zone. These are outlined below, with an assessment of each of the criteria in relation to Taiwan.

1. ’Intensity of the aggressor’s motivations’ (high – the CCP identifies the Taiwan issue as ‘the core of China's core interests’).
2. ‘Attribution of the aggressor’s role’ (rising).
3. ‘Level of aggression’ (rising).
4. ‘U.S. and partner alignment on unacceptable outcomes’ (uncertain).
5. ‘U.S. and partner alignment on deterrent responses’ (low).
6. ‘U.S. and partner proportionate response capabilities’ (weakening).
7. ‘Regional and global support for deterrence’ (high in principle, lower in practice).
8. ‘The aggressor’s expectation of meaningful responses’ (trending up).

Taiwan’s status in the international community and the uncertainty of the US security guarantee narrows its options in all eight criteria, except perhaps attribution of the aggressor’s role, where Taiwan has most agency to improve deterrence.

Taiwan’s detention in February 2025 of a Chinese captain and crew of a vessel suspected of involvement in severing underwater cables is a good example of dark grey action. Denial of the capability (even at the risk of escalation in the form of tit-for-tat detentions) is justifiable on the basis of the strategic importance of the infrastructure in peacetime. Investor confidence in Taiwan as a global IT hub could be dampened if the cable-cutting incidents become more frequent.

Light Grey

‘Light grey’ responses are often more appropriate to Taiwan’s predicament. These include making pressure tolerable through measures that neutralise the effects (through resilience), or by turning the aggressor/victim narrative to Taipei’s advantage. The Philippines’ ‘assertive transparency’ approach – broadcasting video of violent attacks from the Chinese Coast Guard – was found to consolidate domestic legitimacy and attract support from international partners, even if it has less success in changing Chinese policy. Where China’s grey zone actions resemble war rehearsals, the light grey response would frame them as indicative of Beijing’s aggression and its intent to escalate and thereby risk triggering a broader threat to international peace and security. The object should be to flip the narrative from being about Taiwan’s isolation to about the imperative for collective action.

The light/dark grey distinction is not absolute, but the essential difference is that dark grey actions are more symmetrical and light grey actions less so. Dark grey actions confront the problem head-on, imposing direct costs and effecting denial while accepting a calculated risk of escalation. Light grey options instead aim to flip the narrative: exhibiting resilience as proof of government competence (shoring up domestic cohesion) and shining light on events from an angle that casts the shadow of blame on the aggressor.

Acknowledging that Taiwan is already going some way to enact the approaches described above, the following recommendations are highlighted for emphasis, and for their potential for application in other cases:

1. Get ahead of the curve 
   Investing in analysis of grey zone action can not only identify patterns of actions and effects, but also foresee the opportunities for light grey exploitation before the adversary, staying one step ahead. 
    
2. Leverage information exchange for insight and regional coalition building
   Sharing experience with other victims will improve analytical capability and support an international collective action message. Networks of expertise open the door to operational or diplomatic partnerships, overcoming some of the isolation effect Taiwan is experiencing, and illuminating opportunities for horizontal escalation across the wider area of China’s grey zone activities. Attendance at the workshop held for the research for this brief indicates the strong appetite among Taiwan’s neighbours for exchanging lessons on maritime grey zone issues, which can help Taiwan overcome attempts to isolate its policy community. Taiwan could host a regional Network of Excellence, bringing together expertise from both countries around Taiwan and those elsewhere which face grey zone or lawfare challenges. 
    
3. Access a broader knowledge base and a wider diplomatic network
   Taiwan can benefit from expanded links with European governments and institutions where the challenge of grey zone activity is fast rising, leading to new thinking about how best to respond. A RUSI commentary on Russian cable cutting is one example of common operational interests. Elizabeth Braw’s work on Finland’s response to Russian’s grey zone activities indicates that education is an area where resilience can produce deterrence by denial. NATO’s UK-based Maritime Centre for Security of Critical Undersea Infrastructure can share insights on this set of problems. Broader appreciation for Taiwan’s predicament and the insights it has to offer partners facing similar challenges can encourage the international community to support a collective action approach countering efforts to isolate Taiwan. 
    
4. Exploit technology for attribution and cost imposition
   Digital connectivity forms a bridge to multilateral cooperation, with opportunities to pool data and apply machine learning (although the question remains as to what happens when ships turn off their Automatic Identification System to evade detection) and algorithmic tools to identify irregular patterns of activity, and produce predictive analysis. Especially in areas of real-time awareness, such a common operation picture can restrict the scope of ambiguity, aid attribution and have a cost imposition effect by increasing international support in proportion to some kinds of grey zone pressure. 
    
5. Flip grey zone pressure to harden resilience
   According to China, its grey zone pressure is directed not at the ‘compatriots’ on Taiwan, but at ‘separatists’. The more China’s grey zone action can be shown to harm the interests of ordinary people (such as by depressing foreign economic investment), the harder this narrative becomes to sustain. The more Taipei bases the legitimacy of its response on economic and social resilience, the harder it makes it for Beijing to attribute Taiwan’s responses to a ‘separatist’ minority. Taipei’s message should expose China’s bullying and harassment, but also communicate convincingly about why it will not have the desired effect. The more resilience against violence and bullying becomes normalised, the more it entrenches the narrative of China as the reckless aggressor and Taiwan as the responsible victim.  

Taiwan faces an escalating grey zone challenge that could undermine the island’s political cohesion and security. As an open, democratic society facing a powerful adversary with uncertain international support, Taiwan is constrained in its choices about how to respond to grey zone action. Unless China takes unambiguous attributable action that severely damages Taiwanese property, harms its population or occupies territory, the best course of action is mainly in the realm of ‘light grey’ responses – measures that enhance resilience and improve powers of attribution, deny the sanctuary of ambiguity, attach to the opponent the reputational cost of ‘escalation’ and ‘aggression’, bolster social cohesion and lend weight to appeals for international support and solidarity. Taiwan can set an example for others dealing with grey zone action. As it continues to develop approaches such as those outlined in this policy brief, it will strengthen its position to resist pressure and build a broader likeminded coalition that together could deny the gains sought by China and others from exploitation of grey zone vulnerabilities.

© 2025 The Royal United Services Institute for Defence and Security Studies

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