WILLIAM BRANGHAM: We return now to Turkey and this weekend's deadly attack in Istanbul.

What's behind that terror incident and the string of terror attacks in Turkey that have taken place over there over the past year?

We drill down on this with Bulent Aliriza. He directs the Turkey Project at the Center for Strategic and International Studies.

Welcome.

ISIS has claimed responsibility for this latest attack on New Year's Eve. Do you think the evidence will point that they're in fact the perpetrators?

BULENT ALIRIZA, Center for Strategic and International Studies: Well, we do have a statement by ISIS that, in fact, it was responsible for this outrage in Istanbul.

It's actually the first time that ISIS has claimed responsibility for terrorist acts in Turkey, although a number of acts of terrorism have been attributed to ISIS.

The method of operation by the gunman — apparently, it was a single gunman involved — very much suggests that this was ISIS. And, as I said, there is a statement by ISIS that it did it.

And, also, it's important to note that, back on November 2, soon after the assault on Mosul began, Baghdadi, the leaders of ISIS, made a statement, part of which was devoted to Turkey, in which he asked his followers to move against Turkey because Turkey had become, as he called it, an apostate state and, therefore, attacks against Turkey were warranted.

WILLIAM BRANGHAM: Turkey has obviously been suffering attacks not just from ISIS, but also from Kurdish militant groups.

For those people who haven't been following this closely, can you explain this sort of two-front attack on Turkey?

BULENT ALIRIZA: Well, it's exactly as you put it, a two-front attack on Turkey.

Turkey has been grappling with Kurdish separatist terrorism all the way back to 1984. There have been efforts to actually solve the problem, the Kurdish problem within Turkey. But they essentially collapsed in the middle of 2015.

Since then, Turkey has been reengaged in fighting against the PKK, which is the Kurdish separatist terrorist organization. More recently, it's been challenged by ISIS. Now, either of these challenges would be daunting for any state around the world. The scourge of terrorism bedevils the entire world.

But for a country to have to fight two very potent terrorist organizations within its borders, within its capital city, within its most important city, Istanbul, the way that it's been forced to during the past 15, 18 months, is frankly very, very difficult.

WILLIAM BRANGHAM: How has Erdogan been responding to these attacks thus far?

BULENT ALIRIZA: Well, he and his ministers have been saying that the security forces will eventually defeat terrorism.

Now, that's a daunting task, as I said, for any state around the world. Even the U.S. has not actually — with all the effort that is made to deal with terrorism, not got to the position where it says the terrorist threat to the U.S. is over.

Now, in Turkey's case, the fact that it's to the north of two ongoing wars, in Syria and Iraq, where some of the terrorists who are actually also intent on harming Turkey are active makes it so much more difficult for Turkey to try to solve the problem within its borders, given the fact, as I said, that it comes from without.

WILLIAM BRANGHAM: I mean, Erdogan is also, as we speak right now, going through this very lengthy purge of officers up and down the government that he argues were involved in this recent coup attempt. How does that complicate their fight against terrorism within their own borders?

BULENT ALIRIZA: Well, it complicates it immensely, because dealing with these two threats was difficult enough, and then we had a failed coup attempt on July 15.

The government has moved against the followers of Fethullah Gulen that it alleges were involved in this.

WILLIAM BRANGHAM: This is the religious figure who is here in the U.S. that Erdogan argues was behind the coup.

BULENT ALIRIZA: And the Turkish government has asked for his extradition, and that has not happened so far.

It's one of the reasons why there is tension between Ankara and Washington currently. Now, there has been a purge. The attention of the government has been directed at rooting out of the system those it believes to be involved or are somehow implicated or are sympathetic to the coup.

And parallel to that, you have the twin threats, the unprecedented twin threats from ISIS and the PKK, and that is taxing the capabilities of the Turkish state.

WILLIAM BRANGHAM: Syria is also involved in these — I'm sorry — Turkey is also involved in some of the cease-fire that has been going on in Syria.

Is there any sense that you have that, if things were to calm down there and the cease-fire were to really hold, that that might ease some of the pressure on Turkey?

BULENT ALIRIZA: Well, it could, but the Turkish position, which is now coordinated with Russia, is predicated on Turkey's ability to persuade the opposition fighters, many of whom Turkey has been backing for the past five years, to essentially lay down their guns and to accept Bashar al-Assad as — at least for the foreseeable future, as the president of Syria.

And that clearly is going to be difficult for some of the opposition groups to accept. And the ability of Turkey and Russia to actually hold the cease-fire and bring lasting peace to Syria is something that I have grave doubts about.

WILLIAM BRANGHAM: Lastly, very quickly, we obviously have a new administration coming in. Do you think the Trump administration, this will change the calculus for him?

BULENT ALIRIZA: Well, inevitably, there will be a different emphasis once the president-elect takes office.

There has been growing tension between President Erdogan and President Obama. The U.S.-Turkish relationship has been going through a very difficult period. Clearly, there are hopes in Ankara that it will be easier with a new administration. But it's unclear exactly which way the new administration is going to go with Turkey or with the Middle East or, frankly, with the rest of the world.

WILLIAM BRANGHAM: All right, Bulent Aliriza, thank you very much for being here.

BULENT ALIRIZA: Thank you.