There are allegations and analyses that Beijing is using dual-purpose, unmarked vessels around Taiwan to monitor, harass, and assert its presence under the guise of fishing. What is your most up-to-date and in depth assessment?
Strategia-100, Chief Strategist:
Here’s a current and detailed assessment of the evidence, implications, and dynamics around the claims that Beijing is using dual-purpose, unmarked vessels (often under the guise of fishing or civilian functions) around Taiwan to monitor, harass, or establish presence. I’ll cover what the open-source data suggests; where there are uncertainties; what this means in a broader strategy; and possible countermeasures.
What the evidence shows: What’s real, what looks plausible
Multiple recent analyses, incident reports, and Taiwanese government disclosures provide strong support for Beijing’s use of “grey zone” maritime tactics involving non-military or semi-military vessels around Taiwan. Some key findings:
- CSIS “Signals in the Swarm” (Oct 2025)
- Used AIS (Automatic Identification System) data, fishing effort maps (e.g. Global Fishing Watch), overlap with known PLAN (People’s Liberation Army Navy) drill zones to identify anomalous vessel behavior. CSIS
- They started with ~12,000 vessels in Taiwan’s maritime vicinity, narrowed to ~315 vessels flying the Chinese flag & identified as fishing vessels, then flagged 128–209 as likely “grey zone actors” based on behaviors such as loitering near military exercise zones, spending disproportionate time outside fishing hotspots, AIS anomalies (turning off AIS, changing identity, hiding tracks). CSIS
- Incidents of unmarked or “suspicious” vessels
- Taiwan’s Coast Guard (CGA) has detained unmarked vessels without name, home port or registration, inside restricted waters; in one case, a vessel with ~500,000 liters of fuel was found, suggesting logistical support function. Taipei Times+1
- Reports of Chinese fishing vessels transmitting misleading AIS signals — e.g. mimicking coast guard or law enforcement vessel identifiers. Taipei Times
- Taiwan has identified a “shadow fleet” of ~52 Chinese-owned vessels using flags of convenience (registered in third countries) which behave suspiciously: loitering, slow navigation, anchoring near sensitive infrastructure (subsea cables), spending extended time in Taiwanese territorial waters. Taipei Times+1
- Other vessel types with dual‐use / research / militia role
- Research vessels under civilian institutional covers are increasingly active in waters around Taiwan, especially in survey / oceanographic / hydrological data collection, which has both civilian and military value (e.g. mapping seabed, sound propagation etc.). Taiwan’s ICCS reports large increases in scientific research vessel operations, especially along the 12 nautical mile line from Pengjia Islet northward and then along the northeastern coast. iccs.org.tw
- Ferries / roll-on-roll-off vessels are being built or repurposed with landing docks, capable of transporting troops / vehicles; US intelligence (Five Eyes) has expressed concern. ABC
- Persistent pattern of behavior consistent with harassment, probing, and signal testing
- Chinese Coast Guard ships repeatedly entering Taiwan-administered restricted or prohibited waters (e.g. around Kinmen or Pratas/Dongsha), often in conjunction with fishing fleets or militia vessels. tech-consultingstudies.eu+1
- Loitering, slow sailing, anchoring near sensitive areas (cables, islands), regularly tested legal / jurisdictional boundaries. Institute for the Study of War+2Taipei Times+2
Taken together, the evidence very strongly suggests that a subset of ostensibly civilian or fishing vessels are being used for state-directed maritime presence, surveillance, harassment, and possibly logistics/proxy movement.
What remains uncertain / where evidence is weaker
While the patterns are convincing, there are still gaps, ambiguities, or areas needing more verification:
- Attribution and chain of command: It can be hard to prove conclusively that a particular vessel is under direct PLA / state instruction rather than acting independently (economic fishing, private interests, etc.). Some vessels will behave suspiciously, but proving state direction (or orders) is cheaper and riskier.
- Intent vs. capability: Some behavior (e.g. mapping, AIS anomalies) can be for benign scientific or economic purposes; distinguishing dual-use from purely civilian work requires context that is not always public.
- Limits of data: AIS data can be spoofed or unavailable; open-source vessel tracking doesn’t always reveal what is underwater (e.g. sensors, submersibles) or hidden logistics (fuel, supplies).
- Legal grey zones: Much of this activity is nonviolent and legal under international law (or at least not clearly illegal). That gives plausible deniability, and enforcement is difficult.
- Escalation risk: While many of these operations are tolerated for their ambiguity, there’s risk that an incident (collision, refusal to move, interference) triggers escalation. Evidence of such near-misses is less visible publicly.
Strategic rationale: Why Beijing is doing this, and what it gains
Understanding the “why” helps project what might happen next. From what’s evident, Beijing’s use of these vessel types serves several overlapping strategic goals (grey-zone strategy):
- Presence and normalization
- By operating frequently in contested or sensitive maritime zones, using unmarked/fishing vessels, Beijing strengthens its de facto presence. Over time, this can shift perceptions of who controls what, or the limit of tolerable behavior by Taiwan.
- Intelligence gathering and surveillance
- Dual-use vessels (research vessels, fishing vessels with extended loitering) give access to bathymetric data, oceanographic info (currents, seabed features), sensor placement observation, and test reaction times / protocols of Taiwanese forces.
- Harassment and coercion
- Disrupting Taiwanese fishing, interfering with legitimate civilian uses (fishing licenses, navigation, anchorage), creating ambiguity and low-level friction. This imposes cost, uncertainty, and forces Taiwan to commit resources to monitoring and reaction.
- Legal and jurisdictional probing
- Testing the boundaries (how far restricted zones are defended, how Taiwan responds, when something triggers a response). Over time, these actions might be used to justify stronger claims or normalization of broader zones of control.
- Logistics and force preparation
- Dual-use vessels can play supporting roles (fuel, supply, transport, prepositioning) in a crisis—reducing the burden on overt military assets. The development of ferries / roll-on/roll-off / landing docks suggests this. ABC
- Political messaging and deterrence
- These operations send messages: to Taiwan (you are not fully sovereign in practice), to international observers (China is active, competent), and to policymakers (risk of instability). Also may aim to wear down the endurance, vigilance, and political will of Taiwan over time.
Recent trends and shifts
Based on the newest sources (2025), several shifts or escalations are visible:
- Growing sophistication in behavior classification by analysts (AIS-based anomaly detection, matching vessel behavior to known military drill schedules). This increases the risk that operations will be exposed and tracked, reducing their deniability. CSIS
- Increased frequency of incidents: more vessels transmitting fake AIS, more patrols, more research vessels operating in survey roles. Taipei Times+2iccs.org.tw+2
- More systematic use of logistical support vessels (fuel/oil ships) in proximity to restricted waters, which suggests an infrastructure for sustained operations. Taipei Times+1
- Consolidation of the “shadow fleet” concept: vessels with flags of convenience, obscure ownership, irregular operations, used in or near areas of strategic interest (e.g. subsea cables, restricted zones). Taiwan is blacklisting such vessels. Taipei Times+1
Risks and possible consequences
- Risk of miscalculation or incident: With stealthy or ambiguous operations (e.g., changing AIS, unmarked vessels), there’s high risk that Taiwan responds (military, coast guard) and China may deny responsibility—this could lead to escalation.
- International exposure and diplomatic costs: As analyses (like CSIS) grow more public and precise, China risks reputational damage, possible sanctions or counter-measures. Allies of Taiwan, regional powers (Japan, Philippines, U.S.) may increase pressure or support.
- Arms race in surveillance and counter-grey zone capabilities: Taiwan and its partners will increasingly invest in detection, identification, maritime domain awareness; this may drive China to use more stealth, more autonomous or unmanned systems.
- Legal / normative erosion: If China’s version of “freedom of navigation” or “right to fish / research” is normalized in contested areas, it could shift maritime norms in ways that disadvantage Taiwan, or even other countries in the Indo-Pacific.
- Domestic Taiwan implications: These pressure tactics may influence public opinion, political costs, or resource allocation (coast guard funding, dual-use of civilian infrastructure, etc.).
What to watch next (indicators of intensification)
To anticipate further escalation, these are signals to monitor:
- Sharp increase in vessel behavior anomalies (more vessels going dark, identity changes) correlated with PLA exercises.
- Deployment of more dual-use ferries, amphibious logistic support ships, or upgrading of fishing fleet vessels with communications / sensor suites.
- More unmanned or autonomous vessels / drones associated with research vessels or fishing boats.
- More interference with undersea or offshore infrastructure (cables, sensors, mining, etc.).
- Legal changes or regulations by China to claim broader jurisdiction in maritime domains, or Taiwan’s responses (coast guard, legal, diplomatic).
- International reactions—if the U.S., Japan, or others publish more intelligence or increase patrols in sensitive zones, as this undermines China’s plausible deniability.
Strategic implications: Bigger picture
From a strategic standpoint, this is part of China’s broader approach to “hybrid warfare” or “grey zone competition”—an approach well documented in China’s other contested maritime areas (e.g. South China Sea) and increasingly in other domains (cyber, political, legal). The aim is to change facts on the ground (or water) without triggering full-scale war, to stretch rivals’ capabilities thinner, and to normalize outcomes favoring China with managed risk.
For Taiwan, the challenge is asymmetric: Taiwan has fewer resources, must monitor and respond across many domains, must maintain both defense readiness and civilian legitimacy. For China, these operations are cheaper, less risky (politically and militarily), and provide continuous pressure. Over time, such pressure can degrade Taiwan’s sense of security, impose costs (economic, political), and limit its options.
Pathways for countering or mitigating
Given what is known, here are strategic options Taiwan (and its partners) might pursue or be considering:
- Improve Maritime Domain Awareness (MDA)
- Use satellite surveillance, AIS anomaly detection, vessel tracking tied with drill schedules.
- Monitoring of spectral/radar/optical signatures combined with human intelligence.
- Legal and diplomatic pressure
- Publicize incidents, expose vessels using flags of convenience; pressure flag states and ports.
- Use international legal forums / UN / IMO to highlight misuse of civilian vessels.
- Tougher patrols, interception, regulation
- Coast Guard operations to detain, expel, or board suspicious vessels.
- Special focus on logistics vessels (fuel, motherships) that support grey zone ops.
- Hardening civilian infrastructure
- Protect undersea cables, sensors, communication lines.
- Build redundancy; have early-warning / repair capability.
- Allied / partner cooperation
- Share intelligence (e.g. AIS / satellite) with U.S., Japan, Australia etc.
- Joint monitoring or presence operations to raise the costs of covert presence.
- Transparency and defensive posture
- Taiwanese government making public reports of such incidents helps build international awareness and legitimacy.
- Strengthen civilian maritime regulation, licensing, vessel registration transparency.
- Scenario planning for escalation
- Preparing for what happens if a “civilian/dual purpose” vessel incident leads to military skirmish.
- Having rules of engagement, diplomatic back-channels, where possible, to contain escalation.
Assessment: How strong is Beijing’s case, and what might come next
Given the data, Beijing is definitely employing dual-purpose, unmarked vessels (fishing, research, logistical) around Taiwan in grey zone roles. The behavior is systematic, growing in frequency, and increasingly sophisticated (blanking AIS, name changes, pattern matching with drills).
However, up to now these actions have mostly stayed below the threshold for kinetic confrontation—they are harassment, probing, and presence operations rather than overt attack. That gives Beijing plausible deniability and helps avoid triggering a full military response or international condemnation severe enough to outweigh the benefits.
In the near term, we are likely to see:
- An increase in dual-use logistic support near drill zones (fuel ships, supply vessels) to enable more frequent or persistent operations.
- More frequent AIS deception or identity manipulation, particularly timed with large PLA exercises, to test Taiwan’s detection capabilities.
- Greater use of research / environmental / civilian-legal cover operations, particularly in waters near the 12-nm / contiguous zone limits, to push boundaries without overt claims of sovereignty.
- At least some risk of incidents that force a response (e.g. collisions, detentions), which China will try to spin or deny publicly.
Longer term, there is the possibility that Beijing seeks to normalize its presence to the point that Taiwan and regional states must constantly negotiate or contest maritime access, shifting de facto control through gradual, incremental changes.
Strategic theory lens: What this matches, what lessons
From a strategic theory perspective, these operations align with the concept of “compellence / coercion short of war”: using constant low-level pressure to shape an adversary’s behavior, boundaries, and acceptable red lines, without engaging in open conflict (cf. Thomas Schelling, “coercion” and “threats that leave something to chance”). Also, these actions are classic grey-zone operations—ambiguous, deniable, and calibrated to stay below the level that would trigger a large retaliation.
In terms of doctrine, China appears to be operationalizing what Sun Tzu called (paraphrasing) “subtle strategies”—attacking the enemy’s strategy, rather than its cities; winning without fighting. Similarly, Robert Art’s work on limited coercion in international relations would describe this as combining military, legal, economic, and paramilitary elements to increase tension and influence without crossing into open war.
The use of unmarked dual-purpose vessels also connects with systems theory: the maritime domain becomes not just sea lanes, but layers of overlapping actors (civilian, paramilitary, military), information flows (AIS, satellite, optical), legal regimes—and each grey‐zone tactic is one node in a larger network. For Taiwan (and its watchers), resilience comes from reinforcing that network—surveillance, legal clarity, diplomatic alliances.
If you like, I can map out several plausible future scenarios (best-case, worst-case, middle) for how Beijing’s use of these vessels might evolve over the next 2-5 years, plus what Taiwan (and its allies) might do in each. Do you want me to do that?
Strategia-100, Chief Strategist
Three Corporate