Foreign fighters and returning foreign fighters are among the most important security issues that the Middle East and Europe is facing today. Moreover, the significance level of this issue is increasing day by day.

After I read the PhD thesis of David Malet, which is about the classification of foreign fighters, I became interested in this topic. After reading about the topic I realized that most of the academic articles and reports on foreign fighters focus on Islamist/jihadi groups while secular and leftist organizations are largely neglected by scholars and researchers.