Analysis of the practical application of grey zone and hybrid
operations at sea
Siông-Ui, Frederick, TSIAM
詹祥威1
1.

Foreword

Security communities have been using the term "grey zone operations" for over a
decade, initially to describe the challenges China has posed in the maritime context,
particularly concerning Taiwan. These operations, which blur the line between militaryand civilian activities, create substantial di culties for legal authorities in determining
the appropriate responses and procedures. China has increasingly employed grey zone
tactics to pursue various goals, encompassing economic, political, diplomatic, national
defence, and marine security objectives in the region. Importantly, these operations
disrupt the balance of power and force.
Domestic and international laws specify distinct means for addressing irregularbehaviours and criminal actions. Military responses are reserved for acts of war, while
police responses are meant for situations falling outside the scope of warfare. However,
the term "grey zone" underscores the challenge of categorising such behaviours.
Furthermore, democratic nations must adhere to their legal authorisation, and whenrelevant laws lack clarity, grey zone operations can exploit legal ambiguities, creating
potential national security vulnerabilities. On top of this, the hybrid application of bothmilitary and non-military actions adds another layer of complexity.
Amendments to laws such as the "Armed Police Force Law," "Coast Guard Law,"
and "National Maritime Tra c Security Law" have given China a legal foundation tocombine and integrate the use of its military, police, and civilian forces. This provides
China with operational advantages while posing signi cant challenges to the security ofneighbouring countries.
Beyond the legal framework, early detection and warning systems are vital for anation to respond promptly. These systems increasingly rely on integrated technologies,
including satellites, aerial reconnaissance, land-based sensors, and undersea surveillance.
Unmanned vehicles and vessel technologies o er operational advantages by minimising
the risk of detection. We can draw lessons from cases such as the Ukraine War and
HAMAS' attacks on Israel.

1 PhD in international politics, specialising in geo-strategy, wargaming simulation, and maritime

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security. Policy Analyst of Division of Cyber Security and Decision-Making Simulation, INDSR,
Taiwan. Visiting research fellow to the Security Studies Program, Sasakawa Peace Foundation,
Japan.

2.

Grey-Zone Operations Creates Strategic Advantage

Prior to Russia initiated its "special military operation" in Ukraine, the UnitedStates issued warnings to the Western world and Ukraine, alerting them to the potential
for Russian actions. Their intelligence and analysis had identi ed irregular large-scale
troop movements and the positioning of Russian combat units, which indicated anincreasing likelihood of Russia taking military action.2
Despite the accuracy of this intelligence, the US faced a dilemma. On one hand,
they wanted to deter Russia from further action by disclosing this highly accurate
intelligence. However, doing so also put their intelligence sources at risk. Despite theaccuracy of the information, Western countries and Ukraine were inclined to believe that
Russia would remain relatively calm and not initiate another war. As a result, no
preemptive measures were taken.
The intelligence indicated that Russian forces would approach from the north,anking Kyiv from both sides, while others would move to the east of the capital throughthe Ukrainian city of Chernihiv. Some units would also approach Kyiv from the west.3 In
hindsight, this intelligence proved to be relatively accurate compared to the actual
situation, highlighting the meticulous nature of American intelligence.
Interestingly, the Western world, including Ukraine, perceived the actions of the US
as provocations toward Russia rather than as deterrents. Furthermore, Ukraine wasconcerned that these warnings could deter foreign investments, potentially causing
signi cant economic instability in the country. 4 In Europe, especially in Germany, there
was a belief that Western nations could ease the situation through discussions andmeetings with Russian leadership. They were particularly concerned about the possibilityof Russia cutting o the petroleum and gas supply. 5 This misalignment of strategic
thinking between Ukraine and NATO countries allowed Russian troops to gain
advantageous strategic positions and timing.

2 Guardian sta

and agencies, "'Things could go crazy quickly,’ Biden warns on Ukraine as talks in
Berlin fail", Guardian, February 10, 2022, https://bit.ly/405EQEm.

3 Shane Harris, Karen DeYoung, Isabelle Khurshudyan, Ashley Parker and Liz Sly, "Road to war:

U.S. struggled to convince allies, and Zelensky, of risk of invasion", The Washington Post, Aug 16,
2022, https://bit.ly/3QueKro.
4 Shaun Walker, "Don’t panic: why Ukraine doesn’t like western talk of imminent attack", The

Guardian, February 2, 2022, https://bit.ly/46Gezz2.
5 Matthew Karnitschnig, "Putin’s useful German idiots", Politico, March 28, 2022, https://bit.ly/

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flThis paper aims to observe and analyse potential future actions by China at sea inthe context of con icts.

The term "grey-zone operation" aims to pursue strategic objectives "just below thethreshold of traditional armed con icts." 6 Activities that seek to gain an upper hand
before the outbreak of a war can take various forms. These endeavours may involvetactics designed to secure operational advantages in advance of a full-scale con ict. Such
activities encompass a range of strategies, including cyberattacks, espionage, propaganda,
political manipulation, economic pressure, and "military operations aimed at coercion
during peacetime." Since these actions don't involve direct military force, the a ected
party can only respond through diplomatic means and limited military actions, rather
than engaging in full-scale warfare.
The primary objective of these operations is to secure strategic advantages, and apractical countermeasure involves detecting, exposing, and neutralising them tocounteract these advantages. This approach was adopted by the United States before
Russia initiated its attacks. While there was uncertainty about whether Russia would halt
its invasion if detection and deterrence were successful, it should have, at the very least,
provided the defending side with the necessary response time. Unfortunately, therevelation of this information was not taken seriously, and therefore, it did not translate
into a signi cant advantage.
In another recent incident, a terrorist attack was carried out on Israel by HAMAS.
Israel is known for its robust and intricate intelligence network. However, in this case,their intelligence failed to respond e ectively to the initial actions of HAMAS in the greyzone operations in advance. This allowed HAMAS to employ drones and covert attacks
to disrupt communication stations and surveillance towers along the border.
HAMAS acknowledged that the intelligence agencies of Israel were monitoring
their communication channels. They used this acknowledgment as a smokescreen,claiming they had no intention to launch an attack on Israel. The intelligence communityof Israel accepted this claim, thinking it was a genuine statement of intent. 7 Althoughrocket attacks are typically considered acts of war, they provided adequate cover for aground assault in this situation. Most of the casualties resulted from ground attacks
rather than rocket strikes.8 The full-scale ground assaults resulted in over 2,000 casualties
and the taking of hundreds of hostages.
Failing to detect threats is one issue while being unable to defend against drone
detection and attacks is another. HAMAS gained an advantage through intelligencecamou age and prevented potential countermeasures by destroying communication andresponse systems through drone and surprise attacks. Despite the attacks, due to
6 Andrew Dowse, Sascha-Dominik Bachmann, "Explainer:: what is ‘hybrid warfare’ and what ismeant by the ‘grey zone’?", The Conversation, June 17, 2019, https://bit.ly/3ZSDawg.
7 Ronen Bergman, Patrick Kingsley, "How Israel’s Feared Security Services Failed to Stop Hamas’s

Attack", The New York Times, October 10, 2023, https://bit.ly/407r4kE.
8 "At least 250 killed in unprecedented Hamas attack in Israel; prime minister says country is "at

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war"", CBS News, October 7, 2023, https://bit.ly/3QdwWnF.

intelligence misassumptions and communication disruptions, Israel failed to realise theseverity of the situation, which required a timely military response.
These two cases explain that grey-zone operations could not only provide an earlyadvantage before war, but also pursue national interests for actors during peacetime anddisrupt the target country's defensive deployment and resource allocation. Even for
countries such as Hamas-Israel, which are often in battle, it is di cult for drones to be
directly de ned as war behaviours, and it is di cult to determine what kind of
performers are initiated directly—the chaos that can bring and the advantage that can becreated.
3.

If China conducts this action at sea, what would it look like

There are several points worth discussing based on the two cases mentioned above.
First and foremost, signi cant irregular grey zone operations can be used to hidetrue military intentions under the guise of seemingly illegal activities. For instance, if
Russian troops were to conduct large-scale exercises near Ukraine's borders, they might
initially appear as a signi cant threat. However, as time passes and these unusual militaryactivities continue for a long time, they might not be seen as immediate threats anymore.
While vigilance is still necessary, the level of concern tends to decrease. This repeatedpattern can make the defender less on edge and indirectly a ect the operation anddeployment of regular defence measures, and the true intention could be hiding orpretending.
Similarly, the irregular harassment carried out by the Chinese Navy, Chinese Coast
Guard, surveillance ships, and maritime militia has become a regular occurrence.
Through tactics like Automatic Identi cation System (AIS) spoo ng, intelligencedeception, and strategic stealth, these grey-zone operations can o er strategic
advantages, especially in terms of timing, deception, and creating misunderstandings, asseen in previous cases. This strategy thrives as long as these repeated deceptions andoperations can be swiftly transformed into more aggressive actions when needed,
disrupting the opponent's defence plans. Even if it only provides accurate positioning
intelligence and surveillance at the front lines, in combination with reconnaissancesatellites or other methods, it's enough to counter the opponent's covert activities andsave the e ort of conducting investigations.

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Much like the situations in Ukraine and Israel, the Taiwanese military often
considers the possibility of a sudden attack resulting from an extensive Chinese military
exercise aimed at taking control of Taiwan. Consequently, the irregular extensive military
exercises by the Chinese People's Liberation Army (PLA) undoubtedly capture theattention of Taiwan and its allies and lead to a reasonable response. However, there has
been little discussion regarding the potential use of large-scale maritime militia as a toolfor grey-zone operations. Taking a page from HAMAS' playbook, the PLA eet conducts

extensive exercises around the northeast corner of Taiwan, particularly in the Nansei
Islands of Japan. The maritime militia, concealed within shing boats, can damage thepropellers or turbines of Taiwan and Japan's Coast Guard and Navy vessels using
specialised nets, which come to the area for surveillance at the same time. This tactic
allows the PLA to reduce the response capabilities of Taiwan and Japan without direct
military actions in the early stages of a con ict.
While the PLA Navy is engaged with Taiwan, the maritime militia cansimultaneously carry out di erent operations against both Taiwan and Japan, such as
island seizures. Due to Japan's legal and bureaucratic systems, the Japanese government
must deploy various troops based on the di erent crisis stages during the 'island
recapture' process. Coastguards, maritime self-defence forces, and the police handle
di erent aspects, with joint training, communication, and cooperation having only
commenced two years ago.

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From China's perspective, as long as the maritime militia can successfully disrupt
the coordination of Japanese maritime domain forces, they can gain strategic advantages
for the PLA Navy in subsequent operations against the remaining regular naval forces.
Even if the Japan Maritime Self-Defense Force (JMSDF) or Taiwan Navy regroups andghts against the PLA, their e ectiveness could be compromised, with the PLA enjoying
the upper hand. The maritime militias, if not yet eliminated, could launch a series ofguerrilla warfare operations to assist the PLA Navy. By avoiding direct engagement withff

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Fi g u r e 1 , t h e c u r r e n t c r i s i s m a n a g e m e n tmechanism of Japan, at least three units areincluded, "中国による尖閣占拠を想定し図上演習 ⾃衛隊、海保、警察が役割分担を確認", iZa, 2021/06/07, https://bit.ly/40sJ5dv.

One can envision a complex battle eld where the JMSDF and Taiwan Navy must
defend against the PLA Navy while also being cautious about harassment and sabotage
by the militias. The coast guards of Taiwan and Japan must counter these militia actions.
However, identifying friends and foes, planning ring lines and ship movements, selecting
targets, and avoiding collisions can pose signi cant challenges.
Secondly, maritime militias could lay naval mines without detection before theoutbreak of conventional warfare. Although this breaches international laws, it remains
di cult for Taiwan, Japan, and other countries to detect and counteract them. Even
before conducting any operations, ships from Taiwan and Japan might already becompromised, delayed, or damaged by these militia-laid mines. Furthermore, while China
does not have a tradition of 'suicide attacks' to the extent of certain other groups, and nocountry has issued warnings regarding Chinese military adherence to similar doctrines ortraining, if maritime militias were employed to conduct suicide attacks on relevant naval
and maritime vessels in the early stages of a military operation, it could lead to signi cantcasualties and damage that Taiwan and Japan would nd di cult to avoid.
From the HAMAS case, it becomes evident that, through the use of ship disguises,
AIS deception, and communication language faking , it is not as di cult as one might
imagine to approach the coast guard or navy of both Taiwan and Japan in a harmlessmanner on the open sea. Moreover, eets of maritime militia can fabricate situations
resembling accidents. According to the principles of international maritime search andrescue laws, both Taiwan and Japan are obliged to assist vessels that send distress signals.
This, in turn, provides the maritime militia with opportunities to launch attacks or causedelays. As mentioned earlier, maritime militias do not need to achieve victory in formal
military actions. They just need to disrupt the military operations of the target side toprovide a signi cant advantage to the PLA navy.
In terms of more exible application, even if maritime militia doesn't directly
engage as combatants in formal wartime actions, China can still utilise them to disrupt
the military balance in regular warfare or in situations where they are at a disadvantage.
They can achieve this by shifting the gravity of the battle eld or engaging in guerrillastyle harassment, which can disrupt the deployment, tempo, and communication of theregular military forces of Taiwan and Japan, ultimately securing an advantage for China's
navy.

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Thirdly, under the modern mobilisation mechanisms, cruse ships, sh boats withhuge size, could become amphibious ships transporting personnel and vehicles mobilised
via high speed railway from whole Chinese province to eastern part of coastal city. China

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the JMSDF or other actions de ned as international law-de ned acts of war, Japan wouldnd it challenging to respond with 'self-defence actions.'Ocean Shipping Company（COSCO）has been included into mobilisation system evenformed a "strategic projection support eets" under the law and regulation in 2012.9
In a conventional military operation aimed at Taiwan, the maritime militia might
have limited opportunities for direct engagement. Nevertheless, they can play various
roles in supporting military e orts, such as targeting smaller islands for occupation or
assisting in the transportation of supplies for such operations. In essence, maritime
militias have multifaceted roles that require constant monitoring and understanding fromthe very beginning when dealing with them. It is crucial to have a clear understanding
and adherence to rules of engagement, roles, and operational plans among di erent
military units, with the ability to adapt to their actions.
Moreover, it is essential to consider whether there are legal provisions that grant
frontline forces the authority to use force and establish legal responsibilities for
exemptions. These factors are essential in determining the ability to respond swiftly ande ectively to maritime militia activities. E ective communication and coordinatedoperations are vital in responding to maritime militia activities, whether within a single
country, between the defence force and coast guard, or among di erent countries'
defence forces and coast guards. The coordinated mechanism between JMSDF and JCG
has been launched for years, and the Coast Guard and Navy Defence Force of Taiwan
have also established a similar joint operational mechanism. The Coast Guard of Taiwan
and Japan share limited communication channels; however, there is still none between
the Navy Force of Taiwan and Japan.

JMSDF

TNMDF

JCG

TCG

Figure II, shows the intelligence and informationexchange relations between Taiwan and Japan.
JMSDF indicates Japan Maritime Self-Defence
Force; JCG indicates Japan Coast Guard.
TNMDF indicates Taiwan National Maritime
Defence Force, and TCG indicates Taiwan
Coast Guard. The relations between solid lines
sug gest regular and unobstr uctedcommunication channels. The dot lines realise
di culties exist; however, it is still necessary toestablish similar ones. Source : Author.

9 ⼭本勝也，⟨旧くて新しい中国の軍⺠融合：⺠間輸送⼒の戦⼒化⟩，《特集—中国の経済的リ

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スクと「旧くて新しい軍⺠融合」》，CISTEC Journal, 2022.3 No. 198, p. 83

4. Integrated Detection and Aligned Operation as keys to deter ando set
To mitigate the potential impact of these grey zone actions at sea, it is imperative
to recognise the importance of early intelligence detection and analysis, similar to theUnited States' intelligence gathering and disclosure of Russian invasion plans. This
intelligence should encompass both military and non-military activities, especially thosethat are "irregular" or unconventional in nature. Current maritime intelligence andsurveillance e orts are primarily oriented toward military targets, and we need to shift
our focus to monitoring non-military targets.
Regarding the monitoring of non-military targets, it is worth noting that ships over
300 tons are required to have AIS equipment under international conventions. However,challenges can arise from issues like spoo ng, counterfeiting, or AIS shutdown. For
instance, China attempted to evade US sanctions by sending energy transport ships to
Russia through the Sea of Japan, using AIS spoo ng and faking to avoid detection. On
the other hand, ships under 300 tons might not be equipped with AIS, and theirmonitoring relies on satellites, coastal radars, and ship radars, which can have their own
vulnerabilities.
Through AIS spoo ng, counterfeiting, and other means, China immediately
concealed that the transport ship went from the Sea of Japan to Port Vladivostok forenergy supply and trading. 10 However, it was only discovered after the relevant units
compared the tracks afterwards. The purpose of intelligence collection and monitoring isto provide early warning and make early response and deployment adjustments topossible dangers. Through concealment and counterfeiting, the attacker's irregular forces
can easily hide their whereabouts at the rst opportunity and enter a favourable position
early.
The key to improving and strengthening real-time monitoring methods lies incountering potential threats. Much like how the United States publicly discloses
aggressive actions by Russia, we can neutralise the operational advantages our adversaries
seek to gain. To achieve this, Taiwan and Japan should enhance their monitoring
capabilities across the sea, air, and underwater domains. They should collaborate on
sharing and regularly updating voiceprint databases and establishing real-time

 ​​

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Blacki Migliozzi, Alexander Cardia, Muyi Xiao and David Botti, "Fake
Signals and American Insurance: How a Dark Fleet Moves Russian Oil", The New York Times, May
30, 2023, https://bit.ly/43kpAEg.

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10 Christiaan Triebert,

As previously mentioned, ongoing irregular activities can lead to a sense ofcomplacency in defence measures over time. For example, the sudden appearance of large
shing eets in areas with no sh during certain seasons should serve as a warning, or atthe very least, a cause for caution. On the other hand, the intentional separation,
recurrence, and persistent presence of potential threats make it challenging for
authorities to allocate surveillance resources e ectively. Without such precautions, thesetargets might engage in illegal or military activities, such as early deployments,
surveillance, or the placement of underwater explosives. Despite the existing
communication and information exchange between Japan and Taiwan, it is crucial to
avoid redundant and strenuous e orts by national resources.
Information sharing can greatly enhance e ectiveness of search and rescue
operations and humanitarian aid e orts during times of peace. Moreover, utilising sharedplatforms or interconnected UAVs can substantially enhance human safety at sea. Simply
put, the joint Maritime and Aerial Communication Mechanism is crucial for e ective
communication in maritime rescue operations and ensuring human safety, even if we do
not factor in the security aspects mentioned earlier. Japan and China have similar
mechanisms to foster mutual understanding and con dence at sea, so it makes sense forlike-minded countries to do the same.11
Therefore, the solution lies in collaborative innovation, establishing a sharedplatform for underwater unmanned sensors and a web-based system for real-time
information transmission. This is particularly critical for detecting objects that are
di cult to spot, such as UAVs, small vessels, and submarines that may evade traditional
military sensors. Sharing information and creating a common operational picture
signi cantly enhance the e ectiveness of these e orts. Small objects and UAVs, whether
used for surveillance or surprise attacks, can achieve their objectives more easily if notproperly monitored.
Finally, as mentioned earlier, maritime grey zone operations aim to undermine thelegal foundations of democratic nations. In response to this, regional actors should atleast consider amending their domestic laws to classify speci c actions as acts of war
under the scope of international law. Even without uniforms or obvious insignias, speci cbehaviours conducted by maritime militias would still be considered actions of war.12
International Laws do not prohibit countries from launching self-defence as long as one
is considering being attacked. Further, fast and accurately determining the necessity of
11 seeYasuhiro Kawakami, "Japan-China Crisis Communications Are Improving but Face
Challenges", United States Institute of Peace, October 4, 2023, https://bit.ly/3FHwkSu.

12 Yamamoto Katsuya, 'Maritime Security & Safety of the Sea Issues in the East China Sea for

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People Living with the Sea', "Securing Maritime Security and Safety and the Law of the Sea",
Global Ocean Regime Conference, Korea Maritime Institute, November 2023, p. 2

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communication channels. This ensures that both parties can assess and coordinate their
responses e ectively, even adopting a uni ed strategy.

isolating, detaining, arresting, and cutting o communication is necessary while dealing
with the militia. Suppose actions are not considered as an act of war. In that case, thelaws must also recognise the prohibition and authorise the coast guard to use necessary
measures to maintain order within certain areas, including introducing force.
The Maritime Tra c Security Law of China authorises the CCG Units to establish
a "law enforcement area" while necessary even beyond its territory waters, meaning if themilitia were to fail to conduct their mission and be expelled by the coast guard, the CCG
could intervene after receiving an invitation by militia, and establishing area isolate the
JCG or TCG by force.13 Hence, fast and accurate isolating and detaining maritime militia
after recognising the fact of violating the laws is critical to securing the safety andsecurity of coast guards.
5. Conclusion
To conclude, China's maritime militia, operating in the grey zone, can bring bothmilitary and non-military bene ts and advantages to China. From a military perspective,
they can engage in various activities, including monitoring, interference, support, andeven direct participation in military tasks. This maritime militia can e ectively challenge
the legal rights of other countries at sea, disrupt legitimate activities of other nations,and bolster China's presence in the region while engaging in military, policing, andunlawful actions.
For Taiwan and Japan, it is crucial to jointly address these behaviours in theneighbouring waters, and here are the key points they should focus on:
1. Establish a real-time coordination and communication mechanism between
maritime law enforcement units and implement a joint training program to ensure
seamless coordination and consistency in law enforcement across units.
2. Collaborate on reconnaissance and intelligence collection, share information
instantly, and maintain real-time communication. Bilateral agreements should
govern the scope and procedures for sharing and revealing information. This
collaborative e ort should serve to deter and counter China's attempts to use
force in this area beyond the bounds of international legal standards. It is crucial
to make the world aware of China's e orts to undermine international rule of law
and regional stability.
3. Collaborate on the joint development and sharing of surface and underwaterreconnaissance vessels and systems for linking these vessels with traditional

13 see government report of : 翁明賢，⟨中國⼤陸海上交通安全法施⾏之影響及我國因應策略之研

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究⟩，《海洋委員會委託研究》，海洋委員會，2022年08⽉，https://bit.ly/3QDLsH0。

platforms. This can help reduce the cost of continuous and real-time water
surveillance.
4. Amend domestic laws in both Japan and Taiwan concerning grey zone
operations. Specify actions that could be considered acts of war, as well as actions
that, while not acts of war, violate speci c conditions and the rights of nations.
Clearly de ne when the Coast Guard and Maritime Defense Force can intervene,
providing both legal authority to counter illegal actions. Ensure alignment
between the regulations and concepts of both countries to prevent individual
responses to China's actions.

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5. Engage in bilateral war-gaming simulations and discussions on potential
encounters with grey zone operations, conducting joint exercises and training.
This preparation will enable both countries to respond swiftly and e ectively to
any further grey zone operations developed by China.