At this stage in the Syrian war, what are the combatants fighting for? What does it all mean? Journalist Sam Heller, also known on Twitter as @AbuJamajem, watches Syria as obsessively as we do. (Heller’s research interests include power dynamics among Syria’s rebels, trends and debates within jihadist thought, humanitarian issues and governance in Syria.) He explains it all to Kristen Demilio in this second installment of a two-part interview. [Read part one here.]

Q: Care to make a prediction about Aleppo?

Aleppo is tough to say.

Q: The encirclement didn't work, but Russian airstrikes may be tilting the balance.

The rebel supply lines there are pretty strained. You have pressure from all sides. IS from the east and the Syrian Democratic Forces from the west, both encroaching on the Azaz supply route. The rebel control of the Castello road into the city I don't think can be taken for granted. And it wouldn’t surprise me to see that contested further. And then I think it remains to be seen how much of south Aleppo rebels are able to claw back.

Q: Apparently the Russian bombings of south Aleppo were so intense that there's not much left. They basically cleared out of a bunch of villages. Is that really something the regime can hold onto?

I don't think that's necessarily unique to Aleppo or any given area. Apparently, a lot of the areas that have been taken by this Russian-backed offensive – in Latakia, for example – have been totally emptied of rebels and civilians. So the regime doesn’t need to devote significant manpower to controlling a town like Salma, which is now just a ghost town. They can just move their front lines forward, past the town.

But even on more static lines, a lot of these frontline areas have been depopulated. So you're essentially fighting over towns that exist in name-only.

Q: Like Darayaa—800 barrel bombs in one month alone (November 2015)… One town.

In someplace like Darayya, it wouldn't surprise me that you still have some civilians, just because they have nowhere to go.

Q: You've got Mezze Airport right next to it. So they're going to be pummeled into eternity. I remember Darayaa popped back onto our radar a few months ago, and thinking, it's still on the map? It's been so heavily bombed. Jober also comes to mind.

A lot of these areas in the Damascus countryside, though, the people don't have anywhere to go because they're encircled. But if you look at a few places further north, like in the [coastal plains called] Sahel al-Ghab or elsewhere in the northern Hama countryside, there are towns there that people are fighting for but that effectively don't exist anymore. Like al-Latamneh in northern Hama.

These towns are points on a map, but almost all of their residents live in surrounding tree groves, or caves, or have fled further north into relatively safer areas in Idlib. Even there, many live in IDP camps, often in the open air. Pretty desperate circumstances. So what’s left is empty towns, with maybe a few hundred people. It's pretty grim, but I think those are some of the most extreme examples of it.

Q: Certainly Nusra's mixing it up in the south, but they're still pretty much shut out. They haven't displaced the Southern Front, and I don't think they will.

Do you have any sense whether eastern Nusra is fully integrated into southern Nusra? Or are they functioning independently? Because eastern Nusra has a much bigger mouthpiece and media presence, and so you hear a lot more about what they're doing to fight Liwa Shuhada Yarmouk, but I don't know if they necessarily speak for the rest of Southern Nusra, which may not be interested in pursuing eastern Nusra's campaign against the IS elements.

Q: I think that Jabhat a-Nusra in the east and the south understands its place in the pecking order. You also have that oddity of Nusra facilitating the Islamic State's entry into Yarmouk camp. And that seemed to be a question of local youth, some who joined IS, some joined Aknaf. Then just a few kilometers away you've got the Liwa Shuhada/Nusra problem, which blew up recently. And then in Daraa, they came on pretty strong a year ago, and have since kind of died out. They took the Jaber border [with Jordan] alongside the FSA affiliates. Then they kicked the FSA groups out, who subsequently kicked Nusra out of the border crossing.

I think what you see in Yarmouk and the Damascus countryside, you never had a really complete break between Nusra and IS in these areas, in part because of their relative geographic isolation. Likewise, in the Qalamoun until recently, you would see people argue that it was inappropriate to open a front against IS when rebels’ numbers are so few and circumstances are so dire.

In a lot of these discombobulated pockets of rebel control, foreign fighters and more extreme fighters got trapped. They couldn’t get in or out. Of those fighters, the ones who would have leaned more radical in the north and migrated from Nusra to IS, had no real IS to join – in east Ghouta, for example. And so more extreme elements and people sympathetic to IS remained in Nusra's ranks until much more recently, and as a result these local Nusra brigades took a relatively harder line.

Q: It's hard to get a grip on what's going on. It feels like were missing something. Yarmouk itself is a black hole. You have corners that are run by different parties. That's why I got held up today, since I was asking one of our reporters about who controls what.

The last I heard, IS is based in al-Hajar al-Aswad, and they were remote-controlling Yarmouk through coordination with other non-IS local factions. They were able to exert effective control.

Q: The Islamic State got in and then realized pretty quickly that they have no idea how to rule the camp, given the fact that different factions control a corner here and a corner there. It's besieged; how do you feed people? Plus, residents have protested. So IS broke in through the Nusra point, although they still couldn't get food in. So IS comes in and then wonders, why are we here? This is nothing more than a symbolic victory. I think they're looking for an out.

People outside the Damascus area obviously care about what happens in Yarmouk and South Damascus. When IS, arguably abetted by Nusra, was moving on Aknaf Beit al-Maqdis, a lot of people were very worked up and perturbed about it. But south Damascus is just so bleak. It has no real implications for anywhere outside south Damascus, because it’s totally locked in – you're not going to have an offensive come out of south Damascus. It's just hungry people who have been starved into turning on each other in a lot of instances. I think that also informs the position of Nusra there, that they're still mad at Sham a-Rasoul for expelling them from Beit Sahem.

Q: To answer your question, I don't know whether Nusra is coordinating on a national level, but I think Nusra adapts to their circumstances on the ground. South Damascus is a fragile situation; everybody there has staked their turf. They could theoretically create major chaos, but they haven't.

South Damascus sounds like a nightmare. The worst place in Syria.