Aaron Zelen

Aaron Zelen, a senior fellow at the Washington Institute for Near East Policy.

says Islamic State has been severely weakened since its peak a decade ago when it controlled vast territory across Iraq and Syria and carried out brutal killings broadcast on social media.

But, he says, ISIS has continued to use social media to incite and encourage attacks in the West.

Last year, the Pentagon estimated that the Islamic State still had 2,500 fighters in Syria and Iraq.

Scott Newman, NPR News, Washington.

Aaron Zelen, a senior fellow at the Washington Institute for Near East Policy, says the Islamic State has been severely weakened since its peak a decade ago, when it controlled vast territory across Iraq and Syria and carried out brutal killings broadcast on social media.

But he says ISIS has continued to use social media to incite and encourage attacks in the West.

Last year, the Pentagon estimated that the Islamic State still had 2,500 fighters in Syria and Iraq.

Scott Newman, NPR News, Washington.

ISIS never gives up.

As long as they continue to have the will to fight,

they'll use any means necessary to accomplish what they're trying to do.