As the Syrian conflict enters a new stage and Daesh is believed to be almost defeated, there are many unanswered questions in the international arena. The fate of foreign fighters in Syria and the whole region has turned out to be a dilemma for many governments.

Although some Daesh fighters from Syria may have fled or been captured, the doubt around their future remains. According to a recent European report, between 2011 and 2016 more than 42,000 foreign fighters joined the terrorist group and about 5,000 of them were from Europe. This number is huge.

Unofficial data shows that around 70% or nearly 2,000 of these fighters come mainly from France, followed by around a thousand from the U.K. and Germany and another 500 from Belgium. Moreover, some evidence shows that about one-third of the European fighters have already left the conflict zone. Indeed, the outflow towards Syria and Iraq dropped in 2017 along with the territorial containment of Daesh.

In this situation, upon the withdrawal of U.S. troops, the White House has reiterated the need to repatriate these fighters and prosecute them in their homeland. U.S. President Donald Trump urged his European allies to "take back their foreign fighters" in a tweet on Feb. 16, 2019.

The alternative, Trump warned, would be the release of these subjects, with all the related risks. Northern Macedonia was the first European country to make a move in this direction back in August 2018. France and Germany are considering the repatriation of several terrorists as well.

Ankara had already committed itself to prosecute Turkish citizens who had joined Daesh. More recently, after Turkey started the repatriation procedures for foreign Daesh fighters, many European governments had to reconsider their stance despite initial reluctance.

Despite the political reluctance of some governments and the legitimate concerns about their domestic security, it is clear that Europe lacks concrete and effective policies to deal with the problem. Indeed, the repatriation of terrorists is a multidimensional issue entangling several different subjects.

Interestingly from a legal perspective, some countries do not even have appropriate regulations or laws to deal with such criminal cases.

Furthermore, in many cases, there is the thorny problem of concrete evidence against these terrorists. Collecting evidence of warfare or other crimes from nonstate actors is no easy task and overall in some countries, the available evidence may not be sufficient or valid for a trial.

The immediate outcome is that some repatriated fighters could be released once they return home or they could be sentenced for minor crimes. Beyond the judicial procedures, however, the praxis shows several cases of trials and inclusion in rehabilitation programs.

Actually, as the consequences of the long Syrian civil war continue to have repercussions on the international scene, it will take time to address and resolve all related issues.

The situation is indeed more complex than it looks: among those members who left their homeland to fight, there are people who did not have an active role in terrorist activities but adhere to the jihadist ideology.

Those are almost one-fifth of the individuals who joined the war thus their return could increase the danger of terrorist attacks in Europe as they are committed to jihadist principles. In this regard, women and children are sensitive topics for their involvement in indoctrination and propaganda. Hence, these elements have to be considered and monitored carefully since they are highly related to recruitment, proselytizing activities and can worsen the already serious problem of ideological radicalization.

There is no doubt that the risk of escalating terrorist activities in Europe is tangible and the alert is high. Experts mention the "blowback effect" as the possibility that, once back to their countries, the foreign fighters can take action and retaliate.

In other words, after the death of Daesh leader Abu Bakr al-Baghdadi, there is room for a resurgence of terrorism inspired by feelings of revenge.

Along the growing process of ideological polarization within European societies, the existence of potential threats cannot be underestimated. This is why cooperation and exchange of information between governments in the West and the Middle East have become fundamentally important.

* Assistant professor at the University of the Turkish Aeronautical Association, Ankara