Deutsche Welle: Mr Rosiny, British broadcaster Sky News has received data on about 22,000 militants belonging to the so-called "Islamic State" ("IS"). What consequences could the data leak have for the jihadists?

Stephan Rosiny: I'd say you could draw three conclusions, if the data is confirmed to be authentic. The fact that an IS fighter stole the data and broke away from the group points to some level of internal disintegration; there have been other disclosures from other deserters recently. In the last few months we've had several reports about things like desertions, undisciplined behavior and rivalry within the group, all of which indicate that the group is crumbling.

Secondly, the data leak is certainly a blow to IS's global ambitions, because now it will be easier to capture their fighters when they are traveling between IS-controlled territory, or if they travel abroad to commit potential attacks. They'll also no longer be able to hide themselves among refugees, as has happened in some cases previously.

Thirdly, it could be that the data leak ends up strengthening IS in some ways. The 22,000 fighters identified in the documents can no longer go back to their home countries and pretend to be regular citizens, because they are now known to the authorities. This will make it difficult for them to leave IS; they are now more or less at the group's mercy if they want to avoid prosecution. IS could also indirectly benefit from the data leak, because it raises the willingness of those named jihadists to fight - they have nothing more to lose. That's why I think that the authorities really must use the information to offer these fighters deals to leave the group.

The Russian air force has been conducting a campaign against "IS" for several months now. How is this affecting the group's structure and the jihadists' willingness to fight?

It's difficult for outsiders to verify exactly which targets the Russian air force is bombing. There is different information out there and some of it is conflicting. But certainly, the Russians have also hit IS targets. Russia is not the only power currently attacking IS. The Kurdish militia has been carrying out attacks for a long time now in northern Syria. And the Western alliance, the Iraqi military, as well as Sunni and Shiite fighters have also been pushing IS back.

IS has been under increasing pressure in recent months, and it has already lost several cities, territories, revenue sources and important supply routes. That has led to a change in its strategy. It is now cooperating with other jihadist militias to carry out attacks in other countries. It's trying to give its own fighters the impression that the group is still successful and still capable of expanding. But in reality, it is in retreat - IS is losing territory.

Surely this can't fail to have an impact on morale among the jihadists?

That's right. And it's mainly having an effect on IS's understanding of itself. The group's self-proclaimed caliph, Abu Bakr al-Baghdadi, gets his religious and political authority from his promise to create a global Islamist empire. But if that empire starts to fall apart, then it is a massive loss for his legitimacy. For the people living in IS territory, this is only partially good news, because the weaker IS becomes, the more it exerts its power over the population under its control.

He's lost several revenue sources in the last few months: Some oil reserves were taken away, transport routes have been cut off, and the group's "central bank" in Mosul has been hit. In that strike alone, he's rumored to have lost half a billion US dollars. To balance things, he's demanding higher taxes from the population. Necessities such as oil, electricity and water, which he was able to supply quite cheaply up until recently, have now become massively expensive.

"IS" is increasingly expanding in North Africa, particularly in Libya, which is barely a functioning state anymore. What does this mean for Europe? The jihadists are almost on our doorstep.

Its presence in North Africa is the result of defeats in Syria and Iraq. Since then, it's been trying to mobilize other jihadist organizations for its purposes. And it's been working: More than three dozen jihadist groups around the world have joined IS.

IS has always had good relations with Libya - many Libyans helped to establish the group. In Libya and in Yemen, we're seeing a repeat of what already happened in Iraq and Syria: Stateless areas offer IS the ideal conditions for expansion.

What's tragic is that in the case of Yemen, western allies such as Saudi Arabia were partly responsible for creating the power vacuum. It may be that militias associated with IS are expanding in both countries, but I wouldn't view this as an actual expansion of its territory. Because the fighters there won't be able to stop the destruction and the defeat of IS as a territorial state in Syria and Iraq. I think it won't be long before IS is defeated there.

What does that mean for Europe in the context of so-called "sleepers" and unrecognized jihadists?

IS is currently trying to stage a fictitious expansion, on the one hand, by working with other jihadist groups, and on the other, by expanding its sphere of activity. That includes terrorist attacks in other Middle Eastern countries, but also in Europe. It's an aggressive strategy, meant to create the impression that IS is still a powerful force that can attack anywhere.

Al-Baghdadi wants to prove to his followers that he is still pursuing his apocalyptic vision of worldwide Islamization, and that it still makes sense to join him. Another goal of this strategy could be to ignite hatred of the Muslims in Europe, and so motivate them to return to the "Islamic State." IS used to refer to refugees who fled to Europe to escape its reach as infidels, but now it's trying to win them back.

Terrorist attacks in Europe thus serve a double purpose for IS. The leaked data on the 22,000 fighters could now contain the threat somewhat, because it will help intelligence services to prevent attacks. However, the threat of attacks continues to be relatively large.

Stephan Rosiny is a Middle East expert at the German Institute of Global and Area Studies (GIGA) based in Hamburg.