Abstract
This chapter seeks to place the foreign fighters problematic into the view of Czech social sciences. Following conceptualisation and historicisation of this phenomenon, the author focuses on the activities of foreign fighters in the Syria civil war and in particular in the so-called Islamic State (ISIS) Then, he deals with the problematic of the veteran effect and its securitisation, i.e. thematisation as a problem by state security apparatuses, with the effect of legitimising exceptional measures used by Western states to counter the threat thus defined.