China (PRC): Holds the largest footprint, having converted reefs in the "big three" of the Spratlys—Mischief Reef, Subi Reef, and Fiery Cross Reef—into fully militarized, fortified artificial islands with airstrips and radar.
Vietnam: Currently holds the second-most expansive campaign, rapidly creating new land at over 10 sites, adding over 692 acres of new land just between November 2023 and May 2026. Vietnam's efforts focus on building new ports and airfields to bolster its defenses, particularly within the Spratly Islands.
Philippines: Focuses on maintaining existing outposts, such as on Thitu Island (Pag-asa), and challenging Chinese actions, including at Sabina Shoal.
Malaysia: Occupies several reefs, focused on maintaining its existing presence in the southern Spratlys, often with lower-profile activities compared to China and Vietnam.
Taiwan: Occupies the largest natural island in the Spratlys, Taiping Island, which has a runway and pier.
Brunei: Claims a portion of the maritime area but does not occupy any features. [1, 2, 3, 4, 5, 6]
These activities are focused on establishing territorial claims in disputed waters containing vital shipping lanes and rich natural resources. [1]
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Island building in the South China Sea is a contested, ongoing effort by several nations, primarily focused on transforming reefs and shoals into outposts in the Spratly and Paracel Islands. China is the largest builder, creating over 3,500 acres of land from 2013-2017, followed by a rapid, large-scale expansion by Vietnam, which created over 2,200 acres of new land, mostly since 2021.