Vietnam continues modest expansions to its outposts in the Spratly Islands, most recently on Ladd Reef. Satellite imagery from March and June shows that Hanoi has dredged a new channel, which did not exist in older photos, and is expanding one of its two facilities (the other is a small lighthouse to the west) at the feature.

An image from March 18 reveals a channel recently dredged through the southern edge of the reef, with a barge and two large (roughly 160-foot) vessels just north of the mouth of this new entrance into the lagoon. At least 21 smaller ships, all of which appear to be Vietnamese fishing boats, are present inside the lagoon.

A closer look at the barge shows two pieces of construction equipment, likely backhoes or grab dredgers, loading sediment into a waiting vessel after having scooped it off the seabed. This method of dredging is typical of the work Vietnam has undertaken at several of its other occupied features. The Philippines has also started similar work at its facility on Thitu Island. By contrast, China has usually employed suction cutter dredgers in the South China Sea, which can move sediment much more quickly, but at a staggering environmental cost.

The March image also shows that some of that dredged sediment appears to have been deposited next to Vietnam’s small outpost at the northern end of Ladd Reef.

A more recent image taken on June 3 reveals that Vietnam is expanding the northern outpost, building on sediment from the dredged channel. The barge is tied up alongside the construction site, two large ships are visible at the northern end of the channel, and nearly 80 smaller ships both inside and outside the lagoon. Most, if not all, of these seem to be Vietnamese fishing boats.

The new construction involves the installation of a hexagonal platform about 100 feet across. At least one piece of construction equipment, likely a backhoe, is operating on the recently deposited sediment next to this platform. The new structure appears to be identical to expansions built onto four of Vietnam’s other pillbox-like facilities in the Spratlys, at Collins, Lansdowne, Tennent, and Discovery Great Reefs in recent years. Like those expansions, the new building at Ladd will presumably be connected to the existing outpost by a footbridge.

With the new construction at Ladd Reef, Vietnam has made modest upgrades to 21 of its 49 outposts in the Spratlys in recent years. The decision to expand its footprint at Ladd Reef, including with a new channel to facilitate resupply and allow larger vessels to shelter in the lagoon, is of particular interest given recent events. Ladd Reef is the westernmost of the occupied rocks and reefs in the Spratlys. To the southwest lie several undersea banks that China claims as part of the island group despite their being entirely submerged, along with Vietnamese oil and gas blocks that have been the focus of several high-profile spats between Beijing and Hanoi over the last year. Vietnam, the United States, and most of the international community consider that area to be a piece of the continental shelf belonging to Hanoi, but China claims ill-defined “historic rights” to it as part of its “nine-dash line” claim to most of the South China Sea.

Vietnam built a series of small platforms, called “economic, scientific, and technological services stations,” on the underwater banks in the area in the 1980s and 1990s. Despite recent upgrades, those facilities are extremely vulnerable and were reportedly threatened by Beijing as part of its campaign to force Hanoi to abandon oil and gas work in Block 136 last year. This offers one likely motive for Hanoi’s decision to bolster its footprint at nearby Ladd Reef, which could prove valuable as a staging ground for vessels patrolling the outposts and resources to the southeast.

The construction work at Ladd Reef also highlights an important new aspect of Vietnam’s military doctrine in the South China Sea: the use of fishers as a militia force. China employs a maritime militia consisting of fishers from its coastal provinces to bolster its presence and support operations in contested waters without provoking a military response from others. Vietnam learned the difficulty of confronting such a militia firsthand during the 2014 standoff over China’s deployment of an oil rig in disputed waters, when Chinese fishing vessels were called upon to protect the rig’s operations. In response, Vietnam has recruited its own fishers to serve in a similar capacity, though to-date they have been less active than their Chinese counterparts. In this case, the large number of fishing vessels present at Ladd Reef throughout the construction process suggest they might be offering protection and support in an official militia capacity.