in the aftermath of attacks like the one in Paris on Friday, which killed 129 and critically wounded nearly as many, two sets of questions tend to arise: How could this happen? And why did it happen?
The “how” questions are what preoccupy investigators for the first few days after such an attack, as they race to identify the assailants and their collaborators before they can strike again. A complex assault such as the Paris operation usually involves many more people than the perpetrators; as of this writing, seven known assailants have been killed, but authorities in France and Belgium, where the attacks are believed to have been organized, are hunting for additional suspects. Officials will also be looking for weaknesses in France’s defenses. How could so many attackers with explosives have penetrated the country? Clearly there was a major intelligence failure. Border security, surveillance capacity, and coordination between security services will be heavily scrutinized.