Germany had about 1,000 citizens join ISIS. 350 are believed to have came back to Germany, but of that number the government admits to completely losing track of 160 and has no idea where they are other than their last known location was in Germany.
This seems like a serious security hazard as if you were willing to leave Germany to join ISIS, you may be likely to commit terrorist actions at a later date.
https://www.thescottishsun.co.uk/new...rn-from-syria/