A new study from mainland China’s internal security forces offers a glimpse into a future where urban unrest is managed by autonomous machines instead of police in riot gear. In a scenario laid out by engineering experts from the People’s Armed Police Force (PAP), a crowd – incited by rumours following a military takeover of a large city – gathers in a central square to assault key government installations. Their protest meets with a swift response: roadblocks are suddenly deployed, cutting off...