Satellite images from August show new construction on Triton Island, the westernmost island of the Paracel Islands near Vietnam. China has occupied the Paracel Islands since the 1970s, but Taiwan and Vietnam also lay claim to the archipelago.

Just last year, China had fully militarized three islands in the South China Sea, in a move that the U.S. Pentagon assessed was aimed at destabilizing the region and allowing China to extend its offensive capabilities beyond its own shores, by flying fighters, bombers, and more.