Among that number, U.S. intelligence sources estimate that about 3,400 are from Western nations, and 90 nations altogether. They also believe that about 150 people from America have gone to join them.
Depending on the country the people are going from, many of them will be arrested before leaving their own country. Others have been killed while fighting with ISIS, and some may still be fighting beside them.
The fear of many Western nations is that these fighters will return to their own country and try to perform some terrorist act there. Some countries are actively watching the returnees. One of the men, possibly more, in the Charlie Hebdo raid had been in Syria.
* * * * * * *
Source: http://news.yahoo.com/ap-exclusive-20-000-foreign-fighters-flock-syria-211811073.html
* * * * * * *
Graphics: Mine
* * * * * * *
Keywords: ISIS, join, fighters, Western nations, foreign