Rising reefs and shifting power in the South China Sea
Vietnam is rapidly reshaping the map of the Spratly Islands. After years of restrained activity, Hanoi has moved into high gear by expanding tiny reefs and rocks into fortified outposts complete with harbors, helipads, and defensive works. The pace since 2021 has been striking. Satellite analysis shows Vietnam has created thousands of new acres of land across its holdings, lifted basic pillbox sites into larger platforms, and begun laying down infrastructure that allows its navy, coast guard, and maritime militia to operate farther from shore for longer periods. These efforts give Vietnam a broader foothold in one of the world’s most contested maritime zones and arrive at a moment when tensions across the South China Sea remain high.
The Spratlys sit at the crossroads of the Western Pacific. They lie astride shipping routes that carry a large share of world trade and sit close to fishing grounds and potential energy reserves. Multiple governments claim parts of the archipelago. China asserts sweeping claims over almost the entire sea, a position rejected in a 2016 international ruling. Vietnam, the Philippines, Malaysia, Brunei, and Taiwan also claim features in the chain. Against that crowded backdrop, Vietnam’s construction campaign has transformed the scale and capabilities of its outposts, moving from minimal shelters to fortified islands that can host ships, aircraft, and surveillance systems.
The effort also signals a calculated shift in how Hanoi manages its maritime disputes. Vietnam has long tried to balance defense needs with diplomatic caution. Building larger platforms and harbors strengthens its position without frequent confrontation at sea. The new islands do not settle sovereignty. They do help Vietnam maintain a visible presence, protect its fishing communities, and deter coercion by making any attempt to dislodge its forces more costly.
What Vietnam has built since 2021
Vietnam’s reclamation drive has unfolded in waves. After modest work earlier in the decade, activity accelerated in 2023 and surged in 2024. Analysts tracking satellite imagery reported that Vietnam created hundreds of acres of new land in late 2023 and the first half of 2024, lifting its total reclaimed area across disputed parts of the South China Sea into the thousands of acres. By early 2025, estimates put Vietnam’s total reclaimed land at more than three thousand acres, roughly seventy percent of the artificial land China has built across the same waters since its large campaign between 2013 and 2017. That marks a dramatic change from only a few years ago, when Vietnam’s footprint was a fraction of China’s.
The scope of the work spans the entire Vietnamese network in the Spratlys. Since the start of 2025, dredging and landfill have extended to eight features that had not been touched during the current round of building. These include Alison Reef, Collins Reef, East Reef, Landsdowne Reef, and Petley Reef, where small concrete positions have been expanded into true landmasses. New rounds of expansion also resumed at Amboyna Cay, Grierson Reef, and West Reef. With these additions, all twenty one reefs and low tide elevations that Vietnam occupies now include artificial land, a comprehensive buildout compared to the limited structures that stood on many features just four years ago.
The data also show a shift in priorities. Vietnam has devoted a large share of landfill to maritime logistics, carving new harbors into eight of the recently expanded outposts. Prior to 2021, only four Vietnamese features in the Spratlys had harbors. Tripling that number indicates a clear emphasis on keeping more vessels on station and resupplying them locally, which is vital for sustained patrols and for protecting energy exploration or fishermen from harassment.
Key outposts and new infrastructure
Several reefs stand out. Barque Canada Reef has become Vietnam’s largest artificial outpost by land area. Over the course of 2024, it expanded dramatically and now stretches more than four kilometers in length. Construction of a runway at Barque Canada advanced in late 2024, with imagery showing an airstrip of roughly eight thousand feet taking shape. The airfield would be a significant upgrade from Vietnam’s only existing Spratly runway on Spratly Island, which is shorter and restricts the types of aircraft that can operate there. The new strip would enable larger transport planes and surveillance aircraft to stage closer to contested waters, improving reaction time and patrol endurance.
Other features have received substantial upgrades. Discovery Great Reef, South Reef, Namyit Island, Pearson Reef, Ladd Reef, and Tennent Reef have all seen extensive landfill since late 2023. Crews have cut channels, dredged berths, and raised platforms for docks and boat ramps. Temporary helipads have appeared on multiple features. Trenches and coastal defenses ring new shorelines. On some reefs, such as Central Reef and Tennent Reef, new piers and protected basins indicate a plan to host a steady flow of government and maritime militia vessels.
Recent imagery also reveals a repeating pattern of military related infrastructure. Several expanded reefs now include hardened storage depots, often six munitions containers arranged within protective blast walls. Many outposts also show identical clusters of six medium buildings set around three sides of a central courtyard, usually oriented toward the sea. These layouts appear on multiple islands, and some, like Barque Canada, have several sets. Their placement, along with the storage depots, suggests that full length runways are unlikely on other long features such as Ladd, Pearson, Tennent, or South Reef. Barque Canada is likely to remain the only new airfield in the chain for now.
Why the Spratlys matter
The Spratly Islands are small, but the stakes around them are large. The South China Sea links Northeast Asia with Southeast Asia, the Indian Ocean, and the Pacific. Commercial ships transit these waters to carry energy, goods, and raw materials that power major economies. The sea is also a vital protein source for regional communities, and beneath the seabed lie potential oil and gas reserves. Control of reefs, shoals, and waters shapes access to those resources and influences who can deploy patrols or build bases.
International law sets rules for these maritime claims. The United Nations Convention on the Law of the Sea classifies features as islands, rocks, or low tide elevations, and those categories determine what maritime zones they can generate. Land reclamation does not change that legal status. Artificial islands built on rocks or atolls do not create new exclusive zones. A 2016 arbitral ruling involving the Philippines and China found that China’s sweeping claims, depicted as a nine dash line, had no legal basis in the convention. China rejects that ruling, and enforcement in these waters depends less on court decisions than on presence and restraint at sea.
Vietnam’s expansion sits within that legal context. Hanoi argues that it is improving features it already occupies to safeguard personnel and fishermen and to withstand strong storms. The projects also serve strategic needs by creating safer harbors, more storage, and space for sensors and defenses. The result is a stronger administrative and military presence across the southern Spratlys without changing the underlying legal claims.
How China and the region are responding
Beijing has started to speak more forcefully about Vietnam’s construction. In February, a Chinese foreign ministry spokesperson protested work at Barque Canada Reef and labeled it part of what China calls the Nansha Islands. The ministry said Vietnam’s projects were being carried out on islands and reefs that China regards as illegally occupied. That criticism echoed a consistent line that China will defend its claimed sovereignty across the South China Sea.
At a regular briefing, Chinese Foreign Ministry spokesperson Guo Jiakun addressed questions about the Spratlys and Vietnam’s work. He restated Beijing’s position that the features are Chinese territory and warned against construction by other countries.
Guo Jiakun said: “The Spratly Islands are China’s inherent territory. China firmly opposes relevant countries construction activities on illegally occupied islands and reefs and will take necessary measures to safeguard its territorial sovereignty and maritime rights and interests.”
Despite that language, China’s on water response to Vietnam has been limited compared with its confrontations with the Philippines. Chinese coast guard and maritime militia units have harassed Philippine resupply missions at Second Thomas Shoal and stepped up pressure near Scarborough Shoal. Analysts say this focus on Manila may have given Vietnam more political space to expand its outposts without inviting daily interference.
Collin Koh, a research fellow at the S. Rajaratnam School of International Studies in Singapore, noted that Beijing’s attention has been fixed on the Philippines, a United States ally. He said China has an incentive to avoid pushing Vietnam into closer alignment with other claimants or outside powers.
Collin Koh said: “For now much of Chinas bandwidth of attention is directed at the Philippines, and it would rather maintain a stable front with each of the other Southeast Asian rivals in the South China Sea.”
Ray Powell, who directs SeaLight at Stanford University, argued that Beijing appears to accept Vietnam’s quiet consolidation in the Spratlys at the moment, trading it off against the priority of isolating the Philippines.
Ray Powell said: “Beijing has calculated that keeping the Philippines isolated from the other South China Sea claimants is worth more right now than preventing Vietnam from making substantial territorial gains.”
Military balance and strategy
Vietnam’s new landfill and harbors give it tools to operate more persistently. More ports in the Spratlys allow navy, coast guard, and maritime militia vessels to refuel, resupply, and take shelter without returning to the mainland. Harbors at Barque Canada, Ladd, Central, Namyit, Pearson, Sand Cay, South Reef, and Tennent expand this network. This mirrors the logistical advantage China gained after it completed its large artificial islands in the mid 2010s, which host piers, radar, and runways that support round the clock patrols.
Even with better logistics, Vietnam faces a steep disadvantage in numbers and technology compared with China. The People’s Liberation Army Navy and the China Coast Guard field far more ships, and China’s maritime militia can flood contested areas with large fleets of steel hulled trawlers. Vietnam’s fleet modernization has slowed, and its forces must stretch across a long coastline and an extended archipelago. The new outposts help level the operating tempo by cutting transit times, improving maintenance and medical support, and providing positions for additional radar and coastal defense systems.
Defensive works visible on the expanded reefs point toward a denial strategy. Trenches, revetments, and coastal artillery emplacements increase survivability. Hardened storage suggests stocks of fuel or munitions on site. An airstrip at Barque Canada would add airlift and maritime patrol options in the southern Spratlys. These steps make the outposts harder to threaten or blockade and raise the costs of any attempted assault. They do not change the reality that Vietnam could not hold every position against a determined attack by a much larger adversary. They do increase the risks of escalation, which is part of the deterrent effect.
Environmental and legal questions
Reclamation changes the seabed and harms fragile coral ecosystems. Dredging buries reefs under sand and silt and can damage nearby fisheries. Environmental damage has figured in past legal debates about South China Sea activities. Some Philippine officials have weighed legal action over ecological harm from island building, and that track once seemed promising because of the scale of Chinese dredging earlier in the decade.
Vietnam’s entry into large scale reclamation complicates any case that targets a single country for environmental damage. If Manila were to bring a new case that focuses on the environment, it could face accusations of double standards unless it also pursues action over Vietnam’s work. That does not mean a legal strategy is impossible, but it narrows the options and may steer claimants toward cases that challenge unlawful maritime claims rather than ecological harm. None of this alters the core legal point under the law of the sea, which is that new land does not create new maritime rights.
Hanoi frames many of its projects as necessary for safety and support to fishermen who endure stronger storms and more aggressive encounters at sea. That public rationale aligns with the dual use nature of many facilities, such as piers, shelters, and lighthouses. The same structures also improve military logistics. Balancing those two roles will continue to shape how regional governments and outside partners respond to the buildout.
What comes next
With landfill approaching completion at several features, the next phase will likely bring more permanent construction. Expect more work on piers, revetments, air defense positions, and communications nodes. The consistent building patterns seen across outposts suggest a standard plan for garrisons and storage. The runway at Barque Canada appears poised to be the only new airfield in the near term, while longer strips elsewhere are unlikely because of the placement of depots and buildings that now occupy usable corridors.
Other claimants are watching. The Philippines has concentrated on resupply missions and legal and diplomatic efforts, not on large scale island building of its own. Malaysia and Indonesia have stayed quiet about Vietnam’s expansions, and both are unlikely to undertake major reclamation soon. Over time, however, more capable Vietnamese outposts could nudge neighbors to improve their own facilities or patrol patterns. ASEAN and China continue to discuss a code of conduct for the South China Sea, but talks are bogged down on issues unrelated to reclamation, and there is little sign that negotiations will resolve access or enforcement questions soon.
The regional security picture will keep evolving. China is increasing patrols near Vietnam’s outposts while maintaining pressure on Philippine positions. Vietnam is building quietly, avoiding dramatic announcements and limiting statements about its strategy. The United States and several partners have stepped up maritime cooperation and capacity building with Southeast Asian states. The Spratlys will remain a test of presence, patience, and logistics, with Vietnam’s new islands now a permanent part of that contest.
What to Know
- Vietnam has expanded all 21 of its occupied features in the Spratlys into artificial islands since 2021, moving far beyond prior small pillbox sites.
- By early 2025, Vietnam’s total reclaimed land in disputed parts of the South China Sea reached more than three thousand acres, about seventy percent of China’s output.
- Harbors have been added at eight newly expanded outposts, tripling Vietnam’s number of Spratly harbors and greatly improving logistics for longer deployments.
- Barque Canada Reef is now Vietnam’s largest outpost, with a roughly eight thousand foot runway under construction and multiple hardened facilities.
- New infrastructure includes munitions storage depots and clusters of identical buildings arranged around courtyards, plus helipads, trenches, and coastal defenses.
- China has protested Vietnam’s work, but its on water response has been muted compared with confrontations against the Philippines.
- Land reclamation does not change the legal status of maritime claims under the law of the sea, and environmental harms complicate future legal strategies.
- The next phase will bring more permanent facilities across Vietnamese outposts, while neighbors monitor the long term impact on patrol patterns and security.
