Last week, a van was driven into pedestrians on Las Ramblas in Barcelona, killing 13 and injuring at least 130 people, and the driver then killed a 14th victim in order to steal his car and escape. Later in the same day, five men from the same terrorist cell drove into pedestrians in nearby Cambrils, killing one woman and injuring six others. Here, Reader in International Politics Martin Coward discusses these attacks, and how cities can respond to them.