In summer 2015, Turkish authorities captured Belgian Ibrahim El Bakraoui along the Turkish-Syrian border.He was removed to the Netherlands after being suspected of intending to be a foreign terrorist fighter (FTF).Bakraoui was one of the Islamic State-cell suicide bombers at the Brussels airport in March 2016. Bakraoui’s expulsion from Turkey rekindles the need to reexamine the FTF phenomenon and the roles that Turkey is undertaking to combat FTFs.According to the UN Security Council Resolution 2178 (2014) FTFs are individuals who travel to countries other than that of their residence or nationality in order to prepare, plan, or participate in terrorism, such as obtaining terrorist training in conflict zones. In January 2016, the US National Counterterrorism Center estimated the number of FTFs in Iraq and Syria was 36,500, from at least 120 countries, including at least 6,600 Westerners.According to a December 2015 Soufan Group report, the principal sources of FTFs in Iraq and Syria are: Tunisia (6,000), Saudi Arabia (2,500), Russia (2,400), Turkey (2,100) and Jordan (2,000). Among the approximately 4,000 European Union-sourced FTFs, an estimated 2,800 come from just four countries – France (900), Germany (720-740), United Kingdom (700-760) and Belgium (420-516), finds an April 2016 International Centre for Counter-Terrorism – The Hague report. Per capita, Belgium, Denmark, Austria, France and Sweden offer the highest number of FTFs.The risks arising from FTFs are manifold. Besides contributing varying skills to terrorist groups – mainly Islamic State (ISIS) – they may also contribute funds and legitimize the cause. In addition, assuming FTFs return with lingering violent dispositions, they may participate in a “lone wolf” attack, recruit others to undertake a larger- scale attack, develop networks for multiple future operations, participate in the sourcing of funds and weapons and scope future targets for other operatives.It is estimated that ISIS has sent at least 400 FTF to conduct attacks in Europe. Other figures suggest the number of returning FTFs to Europe is 1,200. The November 2015 Paris and March 2016 Brussels terrorist attacks included cells comprised of returning FTFs as well as home-grown violent extremists. Turkey’s borders with Syria and Iraq run some 800 km.and 320 km., respectively. Due to those geographical characteristics, and other factors, Turkey has become a main transit for FTFs in the region.With varying levels of success, Turkey has aimed to disrupt or stop the flow of FTFs.Since 2011, Turkey has been co-chairing the presidency of Global Counter Terrorism Forum (GCTF), a new multilateral counterterrorism body comprising dozens of countries.Through this forum, Turkey has highlighted the threat of FTFs to the international community. In this regard, GCTF embarked on an FTF Initiative, taking steps to adopt best practices policies to respond to FTFs, and aiding in passage of the first UN Security Council Resolution (2178) addressing the FTF phenomenon.Moreover, Turkey has developed two main strategies to stop flow of FTFs. First, it seeks to stop FTFs reaching the first point of entry. No-entry lists of potential FTFs were established bilaterally with other countries as well as other lists through INTERPOL. Additionally, Turkey established risk analysis groups that identify potential FTFs at borders, ports and airports. Too, Turkey has sought for source countries to take measures to prevent departure and travel of FTFs from their countries.Second, Turkey’s second focus is to stop FTFs entering Syria and Iraq.Additional personnel, patrols, and equipment have enhanced security at the Turkey- Syria and Turkey-Iraq borders. The number of Turkish border security forces along the Syrian border rose from 12,000 in 2014 to 20,000 in 2016. New Turkish air defense and reconnaissance units have been added to the battalions, including the active use of unmanned air vehicles. Furthermore, Turkey is establishing a “Syrian border physical security system” that includes construction of 190 km.-long wall, about half of which has already been completed.The threats arising from FTFs in exacerbating current conflicts in Iraq and Syria are coupled by the menace of returning FTFs targeting their home or third countries.Intertwined among these challenges sits Turkey, which will likely continue to face various spillover effects of FTFs in the coming years, along with the resettlement of millions of Syrian refugees, ISIS- and Kurdish-sourced terrorist attacks, geopolitical consequences arising from regional and global powers in the Syrian and Iraqi conflicts, and multifaceted political, social and economic dynamics.Dean C. Alexander is director/ professor of the Homeland Security Research Program at Western Illinois University and co-author of The Islamic State: Combating the Caliphate Without Borders (Lexington, 2015). Lt.Col. (Ret.) Mehmet Nesip Ogun is dean of the Political Science Department of Girne American University in the Turkish Republic of Northern Cyprus.