China’s seizure of an American underwater drone in the South China Sea this month was a reflection of Beijing’s concerns about the growing use of such vehicles in the contested waters and would spur efforts to build up its own military capabilities beneath the waves, military experts say.

Beijing played down the seizure of the unmanned underwater vehicle, which the United States said was operating lawfully in international waters about 50 nautical miles northwest of Subic Bay in the Philippines when it was taken by a Chinese navy ship on December 15, and returned the drone five days later to a US navy ship close to where it had been seized.

…Collin Koh Swee Lean, a research fellow with the Maritime Security Programme at the S. Rajaratnam School of International Studies at Singapore’s Nanyang Technological University, said the “unprecedented” incident was China’s “way of reminding the Americans they shouldn’t even dream about using unmanned systems to continue these military surveillance activities, which it deems detrimental to its national security interest”.

Rather than being an intentional move, premeditated by Beijing, Koh said the drone’s seizure could have been seized “an inadvertent incident caused by local commanders’ initiative”.

He said Beijing was “on the upswing” in the South China Sea after rival claimant and long-time US ally Manila switched to a policy of rapprochement with Beijing under new Philippine president Rodrigo Duter.