Recent imagery appears to confirm a February 21 Reuters report that China has nearly completed structures intended to house surface-to-air missile (SAM) systems on its three largest outposts in the Spratly Islands. The deployment of SAM batteries to Fiery Cross, Mischief, and Subi Reefs would be in keeping with China’s efforts to extend its defense capabilities throughout the nine-dash line. The new structures can be seen in various stages of construction below.

Eight of these buildings are being constructed on each of the three outposts. Each measures about 66 feet long and 33 feet wide. Unnamed intelligence officials who spoke to Reuters indicated that the roof of each concrete building is retractable. This could allow transporter-erector-launcher vehicles carrying missiles—like the HQ-9 SAM systems China has already deployed on Woody Island—stationed within the structures to fire from inside without exposing themselves.

These structures on Fiery Cross, Mischief, and Subi Reefs grant several potential advantages. Unlike the HQ-9s on Woody Island, which are covered only by camouflage netting, those deployed to the Spratlys would enjoy some protection from the elements, especially corrosive seawater. With the roofs closed, the shelters would also conceal launchers from view, thwarting overhead surveillance and preventing adversaries from knowing how many launchers (if any) are present at any given time. Finally, in the event of actual conflict, the structures could withstand indirect strikes or small weapons fire. They are also built very close to the point defenses AMTI identified in December, providing additional protection.

China appears to have begun construction on the buildings between late September and early November 2016. This indicates they are not reactions to the political cycle in Washington, but rather part of a steady pattern of Chinese militarization.  As expected, China’s foreign ministry responded to the Reuters report by claiming that the buildings are “necessary and appropriate” defense facilities.