Researcher: Hybrid tactics likely spreading from Taiwan Strait to the Baltic Sea

Hybrid tactics are "likely" spreading from the Taiwan Strait to the Baltic Sea, says Toomas Hanso, a junior research fellow at the Estonia-based International Center for Defense and Security, after several broken undersea cables were reported in both regions in recent months.
Over the past 18 months, several pipelines and electricity and internet cables have been damaged in the Baltic Sea mostly connecting Finland with other countries in the region such as Estonia, Sweden and Germany. The most recent was on Christmas Day.
In at least two cases, ships dragging their anchors are thought to be the cause. Sabotage is suspected, but difficult to prove – as is typical of hybrid warfare.
Vessels have been flagged from Hong Kong, China and the Cook Islands in the South Pacific. There are also connections to Russia.
But these incidents are not unique. More than 30 fiber-optic data cables connecting Taiwan to surrounding islands have been broken – potentially deliberately – by Chinese ships as political relations have soured in recent years. The most recent was on January 3.
Toomas Hanso, junior research fellow at the International Center for Defense and Security (ICDS), said there are similarities and differences in both cases.

Tactics likely spreading from East to West
"Commonalities between the Taiwan Strait and Baltic Sea seems to be the frequency of incidents and both being geopolitically tense regions. The incidents have had direct impact on national security and communication infrastructure," the researcher said.
"Judging by the frequency in the Taiwan Strait from 2017-2022 and the frequency in the Baltic Sea from 2023 onwards, it looks like a spread of tactics from the Taiwan Strait to the Baltic Sea."
Are Moscow and Beijing cooperating? China (PRC) is assumed to have given tacit support for Russia's full-scale invasion of Ukraine, even if it has never said so publicly. But there is evidence the countries are in other areas. Last October, a Chinese coast guard fleet entered the Arctic sea for the first time in a joint patrol with Russian counterparts, Reuters news agency reported.
The Russian Navy has been "sporadically active" in the Taiwan Strait, Hanso said, often in coordination with the Chinese People's Liberation Army Navy. Russian shipping vessels may also pass through those waters
"But there's no concrete, public evidence suggesting that Russian naval or commercial vessels have directly been involved in cutting undersea cables in the Taiwan Strait. It is also questionable how active China would actually want Russia to be in those waters, Beijing may prefer to limit Russian presence there," he said.
But the case is "stronger" in the Baltic Sea.
"First, in the sense that this tactic has likely been taken over from the Taiwan Strait, where it began to be used frequently before the same practice began appearing in the Baltic Sea. Second, considering the involvement of Chinese ships, Newnew Polar Bear and Yi Peng 3 in the Baltic Sea," the researcher said.
China ramping up hybrid tactics in Taiwan Strait
Hanso said China is using grey-zone tactics and cable cutting is a clearer example than many others. These "grey-zone" activities do not breach escalatory thresholds but still apply coercive pressure, he explained: "PRC practices fit this general pattern."
"While Taiwan often suspects China's involvement, especially given the geopolitical context, the government typically stops short of definitively blaming the PRC without concrete evidence," Hanso said. "If Taiwanese officials were to directly attribute it to the PRC, this could escalate tensions or chances of conflict."
Incidents have spread from the South China Sea, the East China Sea and into the Taiwan Strait since the 2000s.
These include the gradual encirclement and establishment of effective control over disputed island territories, Enforcement of PRC jurisdiction over water and air space surrounding disputed territories, interference with legitimate commercial activity by coastal states, challenges to lawful freedoms of navigation and overflight by the United States and its allies and the undermining the credibility of U.S. alliances, Hanso outlined.
"China is increasingly using grey-zone tactics in the Taiwan Strait," he concluded.
Outlining what Taipei can do, the researcher said: "On preventive measures, there is currently little Taiwan can do to stop Chinese cargo ships carrying out such activities. On increasing resilience, Taiwan can increase the number of cables it has so that cutting one cable does not create a complete outage and cables can be buried deeper to make damaging them harder. Satellite communications are an alternative that Taiwan is investing in to reduce reliance on undersea cables, but these are inferior to undersea cables in terms of transmission capacity."
Wider region watching closely
Hanso said, unlike in the Taiwan Strait, the South China Sea has not seen frequent cable cutting incidents.
"But other countries in the region will certainly be watching closely," he said, citing Brunei, Indonesia, Malaysia, Philippines, Singapore, Vietnam as examples.
"Especially the Philippines which has increasing military cooperation with the U.S. and increasing friction with China in the South China Sea, will probably be very concerned about potential incidents."
Hanso said several incidents between 2017 and 2023, including harassment by Chinese ships of other countries' vessels, has raised concerns about maritime security and protection of undersea infrastructure in the region.
In 2020, the Indonesian authorities called for better protection of critical infrastructure.
Changing maritime regulations depends on China
After the damage to EstLink 2 last month, several countries including Estonia, Finland and Lithuania have suggested changing international maritime regulations to prevent further incidents.
However, this will be difficult and need the agreement of countries such as Russia and China, experts agree.
Hanso said countries in the South China Sea may prefer to prioritize economic ties with Beijing over security.
"All countries in the region probably wish for more secure undersea cables, as these constitute critical infrastructure. However, all countries in the region must also consider their relationship with China," he said.
"If openly supporting a change in maritime law had a negative impact on their trade or security relationship with China, then these countries would have to weigh up whether a perceived increase in maritime security might offset a deterioration in relations with China. Considering that China is the top trading partner of all South China Sea countries except Brunei, they might be hesitant to support a such a law, if it is perceived as "anti-China"."
The situation in the South China Sea has also become increasingly tense in recent years, the researcher said: "Regional countries would probably prefer not to aggravate China and worsen the situation. So, South China Sea countries' support for such a law, might depend largely on how China perceives the law."
NATO's Baltic Sea members will discuss maritime legislation at a summit in Helsinki this week.
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Editor: Marcus Turovski