The terrorist attacks in Würzburg and Ansbach in July were not related to the arrival of so many refugees in the autumn of 2015. Both assailants were already living in Bavaria. But the fact that people, who had been taken in by Germany, then took an ax and a bomb, respectively, and turned on those who had offered help, has highlighted the disturbing side of migration. Many now are asking what kind of people have used the guise of genuine refugees to enter Germany. What will happen next?

Last autumn the security agencies and government representatives responded calmly to these questions. They consistently responded that it made no sense for terrorists to join the stream of refugees traveling to Germany. A journey across the Mediterranean and then over the Balkan route appeared too dangerous and too difficult.

Reality check

Today we know that this assessment was wrong. At the presentation of the annual domestic intelligence agency report at the end of June, the head of the Federal Security Agency, Hans-Georg Maassen, explained that 17 known terrorists traveled to Europe on the Balkan route. According to the Federal Criminal Police Office, the security agencies have over 400 pieces of information indicating that there are soldiers, supporters and members of Islamist terrorist organizations amongst the refugees.

By the beginning of August, 62 investigations were running. Guido Steinberg from the German Institute for International and Security Affairs explained in a recent DW interview: "Before autumn 2015 it was not easy to get to Europe. Of course, terrorists could use fake passports. But fake passports are expensive; fake passports also sometimes get discovered at border controls. But in 2015 there was a different situation in that the potential terrorists actually only had to survive the crossing to Greece. After that there were just open borders, with almost identity or background checks. 'Islamic State' had to take advantage of this."

In any case, the so-called Balkan route was intensively explored and exploited by Islamist extremists. This seems to be the case with Bilal C. who was indicted by the federal attorney general in June. Investigators believe that the Algerian was in contact with Abdelhamid Abaaoud. Abaaoud, one of the suspected planners and assailants in the Paris attacks on November 13 is alleged to have instructed Bilal C. to "explore the Balkan route with respect to the border controls and possibilities for people trafficking." It has been proven that two of the assailants from the Paris attacks traveled this way through Germany to carry out their suicide bombing.

Europol warns of recruitment of refugees

Two Syrians, Saleh A. und Hamza C. who decided to stay in Germany, arrived in summer 2015 after traveling through Turkey and Greece. After their arrival it is alleged that they, together with two other Syrians, planned a large attack on Düsseldorf's Old City. One of the alleged IS-perpetrators was caught in his refugee accommodation in Brandenburg when he went to collect government aid. Near Würzburg and Ansbach photos also emerged from police operations surrounding refugee accomodations. The idea that the very abusers from whom they have been trying to escape have come with them is - for the vast majority of refugees - horrific. Yet Europol has warned that some individual refugees may be susceptible to radical ideas. The European Police Authority describes a "real and imminent threat" that Syrian refugees may be targeted by "radical Islamist recruiters."

German domestic intelligence authorities also recognize this danger. The agency's head, Maassen, has warned against so-called "back-yard mosques." The secret service has observed ultra-conservative Salafist groups targeting refugees. It is alleged that they try to win people over to their ideology by offering help in everyday life. Thomas Mücke, from the Violence Prevention Network, has warned of Islamist extremists using a "charm offensive."

Particularly with under-age refugees, extremely good youth work needs to be in place so that everything can be done to help young refugees integrate successfully. "We have to connect with these young people. If we don't do it the extremists will. And then these youths become so caught up in this environment that you can't reach them anymore," stresses Mücke. Without help there is the danger that such young people may turn to radical Islam when they feel alone and frustrated by daily life.

Refugees could protect Germany

While security risks have been discussed on all sides, most recently experts have said that the German refugee policy offers a chance for heightened security. One such expert is the British author, Robert Verkaik, who has written the recent book "Jihadi John." He claims that the long-term result of accepting hundreds of thousands of Middle Eastern refugees will see Germany protected from terror attacks.

In the British newspaper The Independent, Verkaik wrote that Angela Merkel's government and the solidarity displayed by the German people show that Germany is not in fact in a war against Islam. Out of gratitude and in order to limit the reach of extremists, Muslims in Germany could take part in the work of the security agencies.

This is a similar view to that held by Frances Townsend, former Homeland Security Advisor to former US president George W. Bush from 2004 to 2007. Townsend currently leads the "Counter Extremism Project" and believes that Syrian refugees could be an important source of information for domestic intelligence. But there is another reason why the calculation "fewer refugees, less terror" does not add up, Townsend says. In the refugee camps in and around Syria there is a far greater danger of radicalizing people than in Europe. By taking in refugees, the West has denied "IS" a dangerous source of potential supporters.

The German interior minister has also highlighted the possibilities of cooperating with refugees in his latest package of measures. In the struggle against radicalization and terror, Thomas de Maiziere has created a new point of contact for refugees. There, refugees can pass on information to the German security agencies about potential attackers in their midst.