The standoff began on June 16 when a China Coast Guard (CCG) ship started harassing the Hakuryu 5 and the offshore supply vessels servicing it. Automatic Identification System (AIS) data shows that several CCG ships were deployed in succession to keep up the harassment over the course of the standoff, including the 35111, 45111, 4203, 3308, 5303, and 2305. As ships were relieved, they often traveled to the Chinese outpost on Fiery Cross Reef to resupply before either joining the escort mission around the Haiyang Dizhi 8 or heading back to China.

Exactly how many Chinese and Vietnamese vessels were involved in these two related operations over the course of the standoff is unclear. Those broadcasting AIS—mostly the CCG—almost certainly account for just a small percentage of the total number. Some Vietnamese law enforcement vessels had broadcast AIS during the early weeks of the standoff in July, but soon ceased doing so. In October, Vietnamese Major General Nguyen Minh Hoang announced that 50 Vietnamese and 40 Chinese vessels were involved, while others reported as many as 80 Chinese participants.

Only a few opposing ships seem to have been regularly deployed around the Hakuryu 5 throughout the standoff, suggesting that most of these reported vessels were busing escorting the Haiyang Dizhi 8 or, in the case of the Vietnamese, trying to block its operations. A satellite image from late August captured a Vietnam Fisheries Resource Surveillance vessel positioned between the Hakuryu 5, which was being serviced by an offshore supply vessel (identified via AIS as the Crest Argus 5), and CCG ship 5303. The 56-meter Vietnamese vessel is effectively unarmed and less than half the size of the 138-meter 5303, one of China’s advanced Type 818 Zhaoduan-class cutters which sports a 76-mm cannon.

The Hakuryu 5 broadcast AIS only sporadically during the standoff. Its signal was last seen in Block 06-01 on October 17 and then again in port at Vung Tau, Vietnam, on October 26. This lends credence to social media reports that it had left Block 06-01 on October 22 after completing its drilling work. AIS data shows that the last CCG vessel assigned to the area, the 31302 (since renamed the 2305) left the same day heading north. It joined up with the Haiyang Dizhi 8 and its escorts a day later and together the group returned to Hainan.

As for the Haiyang Dizhi 8, it moved north after the first few weeks of the standoff, extending its survey over a much wider area for the next three months. In hindsight, it is clear that the survey area closely matched a group of oil and gas exploration blocks that the China National Offshore Oil Corporation unsuccessfully offered up for foreign bidding in 2012.

Over the course of the standoff, the Haiyang Dizhi 8 and its CCG escorts made multiple resupply trips to Fiery Cross Reef. While ultimately unsuccessful in persuading Vietnam to halt Rosneft’s drilling work in block 06-01, China’s operations demonstrated that its Spratly outposts now allow it to conduct extended pressure campaigns, increasing the costs and risks for its neighbors to operate within the nine dash line.