Tensions mount in the South China Sea. Satellite imagery has revealed that China has placed military equipment on the islands it has built (or built up) in the vital waterway, despite a pledge by Beijing to not militarize the area. Last week, a Chinese vessel seized a U.S. underwater drone operating in international waters. After criticizing Washington for "hyping up" the incident, China returned the drone to the U.S. Both developments bode ill for hopes that China would moderate its behavior in the contested region and suggest that the incoming U.S. administration needs to prepare for a challenge as soon as it takes office.

During his visit to the United States in September 2015, Chinese President Xi Jinping promised to not militarize the Spratly archipelago, islands and features in the South China Sea claimed by China and the Philippines, and controlled by China. While China has constructed numerous bases and facilities on the territory it controls, it has insisted that they were "mainly for civilian purposes."

Last week, however, satellite imagery revealed by the Asian Maritime Transparency Initiative, a website produced by the Center for Strategic and International Studies, a prominent U.S. think tank, showed that China has deployed military equipment on every island or feature it controls. Six months of extensive analysis uncovered what seem to be anti-aircraft guns, close-in weapons systems (CIWS) to protect against cruise missile strikes, and towers that are thought to contain targeting radar. All would violate Xi's pledge.