The news that the Istanbul attack was carried out by a Russian and citizens of Central Asian states that were once part of the Soviet Union might surprise those who have hitherto seen the group as a collection of mostly Arab fighters with a large Western European contingent.

Yet in fact, Russian citizens — many of whom are Chechens or Dagestanis from the largely Muslim North Caucasus region of Russia — are the largest group of foot soldiers in ISIS from a non-Muslim majority country, and they have played key roles in the group.

According to Turkish officials the attack at Istanbul airport was carried out by terrorists from Russia, Uzbekistan, and Kyrgyzstan and was planned by ISIS’s leadership.

The Soufan Group, a New York-based intelligence consulting firm that tracks “foreign fighters” who have joined ISIS, estimates that 2,400 Russians have traveled to Syria. It placed the number of fighters from Uzbekistan and Kyrgyzstan at 500 each…