Terrorist organizations are known for targeting places that would send some sort of message to their victims. The Sept. 11, 2001 attacks, for example, were targeted at the United States military's headquarters and the nation's financial core.
These are considered "hard targets" — places protected by security measures such as metal detectors, bag checks or cement barriers. Attacking them required extensive planning, financing, and recruiting. But these hard-targets have become more difficult to attack in the U.S. in the years since 2001, with the disruption of groups like al-Qaeda and increased security measures in place.
As a result, experts told BuzzFeed News that "soft-targets" — public spaces where people come together — are increasingly the focus of terrorist groups.
This photo essay by Michael Kirby Smith looks at the middle ground, how our society has slowly accepted the hardening of public spaces.