In 2014, the UN Security Council, in its Resolution 2178, alerted States to the increase in the number of individuals leaving their States of origin to join the ranks of terrorist groups fighting in Syria and Iraq. Likewise, the same Resolution pointed out the danger that these terrorist fighters pose for both international security and their countries of origin. About 20 percent of foreign combatants who have participated in the conflicts in Syria and Iraq are nationals of or residing in a Member State of the European Union and are considered dangerous for their possible involvement in activities directly or indirectly related to terrorism. This chapter will address the evolution of foreign fighters of European origin and how they came to be terrorists in recent years. Secondly, it will examine the elements that justify how foreign combatants pose a threat to international security, and in particular, to European security. It will also examine the difficulties faced by the Member States and the European Union itself in identifying terrorist combatants and applying repressive measures and, finally, the need to concentrate on developing means to prevent terrorist attacks, radicalization and rehabilitation and reintegration of returnees.

El trabajo ha sido fundamentalmente financiado por el Ministerio de Economía y Competitividad Español y el Fondo Europeo de Desarrollo Regional (MINECO/FEDER) en el marco del Proyecto de Investigación con Referencia DER2015-63857-R

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