The Crocus City Hall massacre by ISIS-K shows the resurging prominence of the group — two and a half years after killing 13 U.S. service members at the Kabul airport.

After emerging as a largely peaceful group initially in 2014 in eastern Afghanistan, ISIS-K quickly turned violent. Its advance was halted in 2016 in a Taliban counteroffensive, aided indirectly by U.S. airstrikes, and crippled by infighting between its Afghan and Pakistani commanders, according to a report from the U.S. Institute of Peace.