Tensions between China and Japan have reached a new high after the Japanese government reported a record-breaking 353 days of Chinese government ships entering its contiguous zone in 2024. This aggressive behavior is now matched by Beijing’s deployment of advanced surveillance vessels near Japanese waters, a move that appears to mirror Japan’s own strategic naval positioning in Southeast Asia.
Recent movements of Chinese naval intelligence vessels, including the Type 815A class ships, underscore a deepening surveillance war unfolding across the East China Sea and Philippine Sea. With Beijing now dispatching spy ships into Japanese maritime domains and the Japan Maritime Self-Defense Force (JMSDF) increasing its footprint in foreign waters such as Cambodia, both nations are unmistakably locked in a maritime chess match with growing strategic consequences.
In April 2025, the Japanese Ministry of Defense tracked the Chinese surveillance vessel CNS Yuhengxing (hull number 798) as it navigated from the Philippine Sea into the East China Sea via the Miyako Strait—an area within Japan’s exclusive economic zone. Simultaneously, its sister ship CNS Kaiyangxing (hull number 796) was observed traversing between Taiwan and Japan’s Yonaguni Island, also heading north toward the East China Sea.
Both vessels are part of the People’s Liberation Army Navy’s (PLAN) Type 815A class of electronic reconnaissance ships. These vessels, commissioned between 2017 and 2018, represent a modernized generation of China’s spy fleet. With their distinctive cylindrical radomes and expansive electronic suites, the ships are capable of capturing and analyzing vast streams of electronic, radar, and communications signals—vital tools in Beijing’s broader maritime intelligence efforts.
The Type 815A ships have become a recurring presence in the Western Pacific. Their April movements were not isolated incidents but part of an expanding Chinese surveillance pattern that includes tracking U.S. naval assets like the aircraft carrier USS Nimitz, which was conducting operations in the Philippine Sea at the time.
These Chinese surveillance deployments have raised alarm in Tokyo, especially given the vessels’ proximity to Japanese territory and critical sea lanes. Though no hostile action was taken, the Japanese Navy monitored the spy ships closely, reflecting heightened vigilance as China pushes maritime boundaries.
Just days before China’s spy ships approached Japanese waters, Japan had launched its own controversial maneuver. On April 29, 2025, two JMSDF minesweepers arrived at Cambodia’s Ream Naval Base. Though framed as a goodwill visit and part of ongoing maritime cooperation, the deployment has raised eyebrows, particularly in Beijing.
Ream Naval Base is under close scrutiny, especially after reports emerged in 2023 about China expanding its presence there with infrastructure upgrades and military facilities. Japan’s decision to send naval vessels to the base—one allegedly being outfitted with enhanced surveillance systems—appears to serve dual purposes: bolstering regional cooperation and observing PLAN movements from a strategic vantage point.
This maneuver led to speculation over whether Japan was engaged in intelligence-gathering efforts, subtly countering China’s growing military footprint in Southeast Asia.
The strategic tit-for-tat hasn’t been confined to long-range surveillance ships. On May 15, 2025, four Chinese Coast Guard cutters entered Japanese territorial waters near the Senkaku Islands—administered by Japan but claimed by China as the Diaoyu Islands. This marked the first such intrusion since March 7 and followed a familiar pattern of “rights protection patrols,” as Beijing describes them.
According to reports, the four Chinese vessels entered the 12-nautical-mile territorial waters around the islands one after another. They remained in the area for about two hours before leaving in response to radio warnings issued by the Japan Coast Guard. While the vessels did not engage in hostile acts, the symbolic nature of the intrusion was clear: China does not recognize Japanese sovereignty over the Senkakus and is determined to assert its presence through persistent patrols.
These provocations come amid the larger pattern of Chinese maritime assertiveness. Tokyo’s Ministry of Foreign Affairs revealed that Chinese ships entered the contiguous zone around the Senkakus—a buffer area extending 12 nautical miles beyond territorial waters—on 353 days in 2024. That figure marks the highest level of Chinese maritime activity in the area since Japan began tracking incursions.
The naval back-and-forth points to a growing “gray zone” conflict—a situation below the threshold of conventional war, where states engage in aggressive maneuvers, intelligence collection, and strategic positioning without direct military confrontation. Both China and Japan are leveraging coast guards, surveillance ships, and strategic naval diplomacy to advance their respective national interests.
For China, maintaining a robust presence near the Senkakus and within the broader East China Sea allows it to challenge the legitimacy of Japanese claims while signaling to domestic audiences its commitment to protecting national sovereignty.
For Japan, the response has been twofold: increased maritime patrols and international engagement. Beyond Cambodia, Japan is expanding security partnerships with the Philippines, Vietnam, and Australia, deepening its role in the Indo-Pacific security architecture.
But the shadow war also risks spiraling. The use of heavily equipped surveillance ships near contested waters creates the potential for miscalculation, especially if electronic warfare assets interfere with civilian or military systems. Tokyo has already raised concerns over GPS interference and signal jamming in parts of the East China Sea—activities that Japanese defense officials suspect may be linked to Chinese operations.
Despite escalating tensions, neither side seems eager for open conflict. Instead, China and Japan are engaged in a war of attrition at sea—probing, signaling, and positioning in ways that blur the line between peacetime operations and military escalation.
For China, the goal appears to be normalization: making its constant presence in disputed areas a fact of life, gradually eroding Japan’s administrative control without firing a shot. For Japan, the challenge is to resist normalization without provoking direct conflict—a delicate balance that requires international coordination, strong deterrence, and strategic foresight.
The United States, Japan’s key ally, is increasingly involved in these dynamics. With the USS Nimitz and other Seventh Fleet assets operating in the same region targeted by Chinese spy ships, the Pentagon is closely watching China’s maritime intelligence missions. Washington has repeatedly voiced concern about China’s “unsafe and unprofessional” conduct in international waters.
Meanwhile, Southeast Asian countries are navigating their own tightropes. Cambodia’s cooperation with Japan, even as it hosts Chinese assets, reflects the fluid nature of regional alignments. The Philippines and Vietnam, both at odds with China over South China Sea claims, have welcomed Japan’s security assistance—seeing Tokyo as a stabilizing counterweight to Beijing’s maritime pressure.
The maritime cat-and-mouse game in the Western Pacific shows no signs of slowing. As China continues to push into waters claimed by Japan and others, and as Japan expands its own strategic outreach, the region faces a prolonged era of tension just short of open conflict.
Beijing’s deployment of spy ships to Japanese waters is a clear message: China is watching—closely. But Japan is watching, too. With both nations entrenched in their positions and national pride on the line, the East China Sea is likely to remain one of the world’s most volatile maritime flashpoints in 2025 and beyond.
