U.S. officials believe that ISIS is providing tactical expertise and training facilities to these foreign fighters — building the infrastructure for foreign terrorist operations. Moreover, Baghdadi and other top leaders are said to have issued multiple statements over the past two years threatening international attacks.

In the view of these officials, ISIS could attempt an attack outside the Middle East soon, and several plots have already been disrupted. But analysts believe that the group is focused now mostly on battles within Syria and Iraq.

The group has established a secure haven in Raqqah, a city of about 220,000. Its fighters control the roads in and out. They sell the region’s oil and natural gas resources to finance their operations, supplementing revenues from kidnapping and other criminal activities. U.S. officials believe ISIS is now self-financing and no longer needs donations from wealthy supporters in the Gulf.

As its name implies, ISIS seeks to mobilize Sunnis in both Iraq and Syria. The Iraq branch is battle-hardened from its years of fighting under Abu Musab al-Zarqawi against U.S. military occupation. Their Iraq force is smaller than in Syria, probably numbering in the hundreds, but it has a tight command structure and has spearheaded Sunni attacks against government troops in Fallujah and other neighborhoods west of Baghdad.