An estimated 300 Americans attempted to join the Islamic State and other radical Islamist groups in Iraq and Syria, including a small number who rose to senior positions, according to the most detailed report to date on this issue.
So far, 12 of those Americans have returned home, yet none has carried out an attack on U.S. soil,* according the report released Monday by George Washington University's Program on Extremism.
Caveat: OSINT can have limitations.


The George Washington University team scoured online material, reviewed court records, spoke with government officials and interviewed some of those who returned to the U.S. after joining ISIS.
Around 50 Americans were arrested as they tried to leave the country, and never made it out of the U.S. The report was able to document 64 individuals who did reach Syria or Iraq.
*
Of the 12 Americans who returned, nine were arrested and remain in custody, the report said. Two others are known to law enforcement, but have not been detained, it added. The 12th man went back to Syria a second time and carried out a suicide bombing, the report said.
https://www.npr.org/sections/paralle...eturned-to-u-s