The US and Chinese militaries are starting to test swarming drones – distributed collaborative systems made up of many small, cheap, unmanned aircraft. This new subset of independently operating or “autonomous” weapons is giving rise to new strategic, ethical, and legal questions. Swarming drones could offer real advantages, including reducing the loss of both human life and expensive equipment in battle. But they also come with potential dangers. There is already great international concern about deploying weapons without “meaningful human control.” Proliferation is another danger, and a problem that could be particularly acute in the case of swarming drones. The risks posed by swarming drones should be considered sooner rather than later, before their destructive potential reaches maturity. Read this free-access article from the subscription journal.