The terrorist plot to kill hundreds or maybe thousands of people at a Taylor Swift concert in Vienna has surprised many, not least the tens of thousands who had bought tickets for the event. But it shouldn’t be a shock at all.

Groups like al-Qaida and ISIS, which inspired the teenage planners of this murderous attempt, are still around, even thriving. And pop concerts—attended by many young people, especially young women freely wearing what they want and having too much fun to notice suspicious things around them—are among their favorite targets.

In 2017, an ISIS suicide bomber attacked an arena in Manchester where Ariana Grande was performing, killing 22 people and injuring more than 1,000. This past March, ISIS terrorists carried out a mass shooting and knife-slashing at a huge concert hall in Moscow, killing more than 145 people and injuring more than 550.

Then, of course, there was Hamas’ rampage at Israel’s Nova music festival, killing 364 and kidnapping 40—the first act of the terrorist group’s Oct. 7 assault across the Gazan border, killing about 1,200 Israelis and taking more than 200 hostages in all. It was the deadliest concert attack in history.

Hamas has no formal relationship with either ISIS or al-Qaida. But Bruce Hoffman, a counterterrorism expert at the Council on Foreign Relations, noted in an email that there are ties among them. Al-Qaida has always had an alliance of sorts with Iran, which supports Hamas and other Islamist militias throughout the Middle East—including Hezbollah, which trained al-Qaida in the 1990s. “Without their tutelage,” Hoffman says, “it is questionable that........

© Slate