The Defense Department announced on Friday that the U.S. military killed an ISIS leader in a blow that “sets them back for a day, a week, a month,” Defense Secretary James Mattis told reporters.

A military drone struck Abu Sayed, the “Emir” for ISIS-Khorasan (ISIS-K), on July 11 in Kunar Province, CNN reported. Sayed was the third ISIS-K leader to have been killed by the U.S. military since July 2016.

The commander for U.S. Forces in Afghanistan Gen. John Nicholson pledged to annihilate ISIS-K. “This operation is another success in our campaign to defeat ISIS-K in Afghanistan in 2017,” Nicholson said in a statement. “Abu Sayed is the third ISIS-K emir we have killed in the last year and we will continue until they are annihilated. There is no safe haven for ISIS-K in Afghanistan.”

The last emir before Sayed was Abdul Hasib, who died in a military raid in April. That raid, conducted by both U.S. and Afghan forces, killed 35 ISIS fighters in addition to several other ISIS-K leaders.

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