How is the plot to attack a Taylor Swift concert related to ISIS-K?

Three Taylor Swift concerts were canceled in Austria this week, after authorities foiled planned attacks on the venue.

Three young men are now in custody, and at least two of them recently pledged allegiance to the Islamic State — specifically an affiliate group known as ISIS-K.

This isn't the first time Islamic State-related groups have been tied to attacks in Europe — over 140 people were killed in an attack on a Moscow concert hall earlier this year, and an explosion at an Ariana Grande concert in 2017 killed 22 and injured more than a thousand.

So - what exactly is ISIS-K, and how should we think about their presence in Europe?

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