US backed rebels have taken back Tabqa and the nearby dam from ISIS.

Tabqa as seen from the Tabqa Dam. Reuters. 

US backed rebels have taken back the town of Tabqa and the nearby Tabqa Dam from ISIS. Reuters. Taking the city is seen as a major victory for the rebels and the US government who will use the area to advance on the de-facto ISIS capital of Raqqa. The assault had begun last March with an airborne assault involving rebels and US Special Forces. Raqqa is now mostly surrounded and cut off from the rest of ISIS territory, with the only escape being via boat over the Euphrates. 

My Comment:

This is a major victory for the United States and our allies. Tabqa was a major defensive post for ISIS and losing it will make it much easier for Raqqa to be surrounded and destroyed. With Tabqa liberated it looks like Raqqa is in a salient. Once the offensive starts again, the rebels will be able to advance to the east and completely cut off the city. 

Raqqa's supply lines have already been mostly cut off. The north, east and now west are under control of rebels and the Kurds. The bridges across the Euphrates have also been destroyed leaving boats the only real option to escape the city. If the battle of Mosul is any indication, those boats will now be a primary target for coalition air forces. Once those boats are gone then ISIS will have nowhere to run and will have to make a final stand in Raqqa. 

The battle of Raqqa will be brutal and I don't know if the local forces are up to the task. Sure, we are arming the rebels and Kurds fairly well, even over the objections of Turkey. But the fight for Raqqa is going to be extremely tough urban fighting. Though Raqqa doesn't have anywhere near the population of Mosul in Iraq, the fighting will be much the same. I just don't think that the Syrian rebels and Kurds will have all that much experience with urban fighting. In Mosul, the Iraqis do have plenty of experience with urban fighting, but even their it is taking months to liberate the city...

It was a good thing that the Tabqa Dam was captured from ISIS before Raqqa. Though the Tabqa Dam is much safer than the Mosul Dam, there was always a chance that they could blow up the dam, which would flood the countryside. Right now ISIS couldn't do it because Raqqa is downstream from the dam, as well as ISIS outposts in Deir ez Zor and other areas, so destroying it would obviously be counter productive. But if Raqqa had been taken first, they might have thought doing so was worth it as a final act of revenge and brutality. 

I do wonder how important Raqqa actually is for ISIS though. It seems likely that most ISIS leadership has fled the city for safer places. The problem is that ISIS really doesn't fully control any other larger cities. They still control bits of Mosul but that city is cut off and is on the verge of being liberated. The only other real option is Deir ez Zor, but that city has never been fully under control of ISIS with the Syrian government having major forces in the area, despite the very long siege. Still, if Raqqa is lost, it's not like there aren't other places for ISIS to flee too. 

Still, losing Raqqa would be the biggest defeat for ISIS in the entire war. Even worse than losing Mosul. Raqqa is the capital of ISIS and losing it would essentially end the claims that ISIS is an actual state. It would be a huge propaganda blow to ISIS and would be a major signal that they were finished as an actual state. They would lose so much prestige and power that they would cease to exist as anything resembling a real state. 

Still, even after the fall of Raqqa and Mosul, ISIS will still be a threat. They still control large swaths of the countryside in Syria and Iraq, control most of Deir Ez Zor, have outposts in Egypt, Libya and Afghanistan and will probably act as a more traditional terrorist group as their numbers and territorial possessions decrease.  

Of course a major problem is that many of these ISIS fighters will try to escape from Syria and Iraq as the major cities fall. There is a good chance that many of these fighters will return to their home countries to sow chaos and destruction. Even after ISIS loses their territorial holdings, they will still remain a major threat, perhaps for an entire generation...