In September 2014, the U.S. began a massive bombing campaign in Syria to weaken ISIS' firm grip on parts of the country. Over a year later, what is the state of ISIS? This video from The Atlantic drills down into the available data to assess its territorial reach, the size of its forces, and the number of people living under ISIS control. For instance, the CIA reported that, in 2014, there were 30,000 ISIS fighters -- roughly the size of Bulgaria's military. Newer estimates from the Pentagon say ISIS now has about 15,000 active soldiers.
RELATED: Why Osama Bin Laden Would Have Hated ISIS
This is not meant to underplay the group's potential for violence or influence. As the attack in San Bernardino illustrated, there's a growing trend of people around the world carrying out terrorism and declaring allegiance with ISIS. These attackers may not even have formal ties to the extremist group, making it particularly difficult for authorities to track.