China's Navy Tweaking Tactics To Undercut Taiwan's Defenses

The frequency of such situations has risen from 46% of days last year to 74.7% this year. More critically, when over 10 PLAN vessels are active, Taiwan would deploy over half of its major combat vessels, with such occurrences nearly doubling from 6.6% of days last year to 11% this year.

The situation has disrupted the regular maintenance schedule and shortens service life of the surface fleet. As of July 2023, 14 (53.85%) of Taiwan's combat vessels had missed scheduled maintenance . With the increased frequency of PLAN activities this year, further disruptions to maintenance schedules appear likely.

Second, the PLAN and its anti-submarine helicopters have intensified operations in areas crucial for the force preservation of the Taiwan Navy during wartime. MND has released a significant increase in PLAN anti-submarine helicopter activities in Taiwan's eastern waters this year. The following figure shows the trend in these PLAN activities.

To compare differences in operational areas, the authors have drawn a grey line from Taiwan's southernmost point at Eluanbi to Yami Island, the northernmost point of the Philippines. This line marks the boundary between Taiwan's southwestern and eastern waters. Additionally, the Yonaguni Channel divides the eastern waters of Taiwan from the northeastern waters.

The frequency of these helicopter activities in Taiwan's eastern waters has surged this year. In 2023, these helicopters operated on 90 days, with 33 days (36.7%) in the southwestern waters and 59 days (65.6%) in the eastern waters. In 2024, up until August 25, there were 64 days of activity, with 17 days (26.6%) in the southwestern waters and 58 days (90.6%) in the eastern waters of Taiwan.

The increased activity of these helicopters in Taiwan's eastern waters has several implications. First, their presence suggests that PLAN warships are nearby, as these helicopters take off from such vessels. Second, these operations likely involve practicing or executing anti-submarine warfare (ASW), targeting underwater activities by Taiwan, the United States, or Japan. Third, the helicopters may be coordinating with PLAN submarines for operational training, enhancing their ASW capabilities in these waters.

The impact of the helicopter activities in Taiwan's eastern waters is the significant threat they pose to Taiwan's naval force preservation zone during wartime. Taiwan's major naval bases are located at Zuoying in Kaohsiung, Magong in Penghu, and Su'ao in Yilan, with two of these bases directly in the path of a potential PLA assault.

As a result, the Taiwan Navy would relocate its fleet to the eastern waters of Taiwan, rather than remaining in the Taiwan Strait, during wartime. PLAN anti-submarine helicopter operations in these waters appear to be aimed at the preparation of the battlefield within Taiwan's wartime preservation zone.

By searching for and engaging submarines from Taiwan or other countries, or by coordinating with PLAN submarines to attack Taiwanese naval vessels, these activities seriously threaten Taiwan's ability to preserve its naval combat capacities.

Third, the frequency of PLAN vessels passing through the Yonaguni Channel has significantly increased, likely due to Taiwan's potential new submarine base in Su'ao, Yilan. Japan's Ministry of Defense reports a noticeable rise in the number of PLAN destroyers and frigates transiting these waters this year (as of August 25). The following table provides statistics on the activities of PLAN destroyers and frigates, as published by Japan's Ministry of Defense.

Since 2021, PLAN warships have been transiting the Yonaguni Channel, with 18 recorded transits as of August 25 this year-double the nine transits recorded for all of 2023.

The increased activity of PLAN warships in the Yonaguni Channel this year likely stems from Taiwan's indigenous-built submarines to be in service and the potential establishment of a new submarine base at Su'ao, Yilan.

Previously, Taiwan's only submarine base was at Zuoying in Kaohsiung, directly facing China. Given the need for a base on Taiwan's eastern coast for wartime force preservation, the timeline is significant: Taiwan began the construction of the new submarine in November 2020 , launched her in September 2023 , and reports from March 2024 suggested plans for a new submarine base in Su'ao, Yilan.

As previously noted, Taiwan's eastern waters are crucial for preserving its naval forces during wartime, with submarine warfare underwater as a key area of engagement between the PLAN and Taiwan Navy. Therefore, the potential submarine base at Su'ao, Yilan, is strategically vital for Taiwan's defense.

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This strategic importance likely explains the PLAN's intensified activities in the Yonaguni Channel, aimed at increasing familiarity with the local environment and hydrography, laying the groundwork for future operations against Taiwan's submarines.

In conclusion, the PLAN's operational adjustments this year carry significant military implications. They indicate China's continued efforts to strengthen its preparations for military operations against Taiwan and suggest that the PLAN is strategically positioning itself in response to Taiwan's naval strategies and recent developments.

Based on the above trends, two suggestions are proposed. First, while emphasizing asymmetric warfare for decisive battles, Taiwan's conventional military assets should receive more attention.

Given China's attrition strategy involving jurisdictional matters, a lack of major naval vessels could allow China to dominate the waters around Taiwan and disrupt maritime transport to its offshore islands. This could replicate China's blockade of Philippine resupply missions at the Second Thomas Shoal, which anti-ship missiles alone cannot effectively counter before a war begins.

Second, in response to China's ASW activities, Taiwan, Japan, the Philippines, and the United States should enhance their coordination in these critical waters. This coordination does not need to involve formal military alliances or sensitive information exchanges but could take the form of informal collaboration.

For instance, multiple countries could conduct simultaneous naval training in different but adjacent designated waters or rotate training in the same area. Such measures would increase operational pressure on the PLAN and could even disrupt its ASW operations.

Cheng-kun Ma (...) is a professor at the Graduate Institute of China Military Affairs Studies at National Defense University, ROC, and the Director of the Research Project on China's Defense Affairs (RCDA). Tristan Tang (...) is a research associate at the Research Project on China's Defense Affairs (RCDA).

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