China has maintained an almost constant militia presence around Thitu Island, the largest of the Spratly Islands occupied by the Philippines, for over 450 days according to satellite imagery analyzed by AMTI. China first deployed militia vessels around Thitu in December 2018 in response to Philippine efforts to repair the island’s runway and undertake other upgrades. Since then, the militia fleet has fluctuated in size but rarely, if ever, disappeared. As a result, the Philippines has made very little progress on its planned upgrades. But there are signs that could be changing.

AMTI reached this conclusion after examining satellite imagery from PlanetLabs collected between December 2, 2018, and March 2, 2020. For consistency, vessels were only counted inside a 32-square-nautical-mile area covering the reefs and sandbars to the west of Thitu, where most of the militia fleet congregates. Images which included less than 50 percent of this target area or had more than 50 percent cloud cover were excluded. In total, AMTI was able to count vessels on 208 out of 459 days. This reveals an average of 18 Chinese ships around Thitu each day. These counts indicate the minimum number of Chinese ships present on a given day. Many vessels likely went uncounted because they were under cloud cover or outside the frame of the images.

The militia initially deployed around Thitu at the start of December 2018. Their numbers peaked later that month when the Philippines’ brought in the supplies needed for their repairs. They spiked again in February 2019. By April, the Armed Forces of the Philippines publicly acknowledged that it had monitored hundreds of Chinese boats around Thitu. The number of militia ships then shrank for several months. In early June, Philippine special envoy to China Ramon Tulfo insisted that Beijing had withdrawn all its boats as a gesture of goodwill. This was not true, and within a couple weeks their numbers exploded again and remained elevated through mid-July.

Militia boats have remained near Thitu nearly every day since. Their numbers surged again in August, September, and December. For instance, higher-resolution imagery collected by Maxar on December 18 reveals 88 Chinese vessels loitering near the island. As usual, the evidence indicates that these ships are not fishing. Most are trawlers, and yet they sit stationary, clearly not trawling. A small number are falling net vessels, but they have no gear deployed. VIIRS imagery from this period shows no evidence of lights being used for night fishing. All of this is consistent with the behavior of the fleet since December 2018—the “fishing” ships around Thitu are engaged in surveillance and harassment, not fishing.

And as usually happens when their numbers spike, the militia boats were accompanied by a government vessel, in this case the Shuwu-class China Coast Guard 5103. This same ship, then known as China Marine Surveillance 84, participated in the 2012 standoff with Philippine vessels at Scarborough Shoal.

This surge continued through the first two months of 2020 with the Philippine military reporting that it had monitored 136 unique Chinese vessels near Thitu in that time. A February 13 image from Maxar captured nearly 40 militia ships, this time accompanied by the Xiang Yang Hong 9-class China Coast Guard 5401.

The same image shows four stationary vessels, three of which are lashed together, at the western edge of the lagoon. This is just next to what is often called Sandy Cay—the farthest from Thitu (and closest to Subi Reef) of several sandbars that were created by sediment drifting from China’s newly-built artificial island on Subi. The ships, which do not appear to be trawlers like most others in the flotilla, arrived in this position by January 16 and did not leave until at least February 25. This appears to be the first time that individual vessels have stayed in one place for so long, though what they were doing for those six weeks is unclear.

Meanwhile the Philippines has slowly made progress on its upgrade work at Thitu after repeated delays. Officials in Manila have consistently blamed the delays on bad weather, but it seems likely that the constant Chinese militia presence has played a role. The first barge of materials to repair the runway arrived in May 2018. By that December, the government had shifted its focus to building a beaching ramp north of the runway to more easily bring in supplies and equipment for the repair work. This is what seems to have provoked the initial Chinese militia deployment. By January 2019, satellite imagery showed that the Philippines was undertaking more ambitious dredging and landfill work than needed to build a ramp. More recent imagery sheds light on the ongoing construction.

Imagery from June 6, 2019, shows two barges pulled up to Thitu. One was offloading sand and materials to fill in the runway—a job that had been on hold for months. The other was offloading supplies at the beaching ramp, which Defense Secretary Delfin Lorenzana would declare 60 percent complete a month later. The image also shows that the area north of the beaching ramp, where several channels were dredged at the start of the year, had been cleared of sand. And most telling—a retaining wall had been built to separate these dredged channels from an area of newly-created beach to the east.

By October 3, imagery shows the collapsed runway mostly filled-in with new sand. Meanwhile further dredging was underway in the area north of the beaching ramp and a channel was being dug from this area to the edge of the reef. The beaching ramp had also expanded, presumably from sand deposited there by the dredgers.

More recent imagery from February 13 provides an update on this work. The runway repairs are continuing slowly. But most of the dredging to the north is complete and it seems clear that this area is being turned into a small harbor. This should improve the quality of life for Thitu’s civilian fishers, make resupply easier, and facilitate other planned construction like a desalination plant, solar arrays, and improved housing. It could also allow the Philippine Navy and law enforcement agencies to rotationally deploy vessels to Thitu for the first time. How the Chinese militia would respond, and whether they will continue to menace Thitu once the repairs are complete, are open questions.

AMTI explains the role of China’s Maritime Militia in this short explainer video featuring high-resolution imagery from Thitu Island and Loaita Cay: