Following statements from US officials that they wanted a military offensive launched against the ISIS capital city of Raqqa during the ongoing Iraqi invasion of ISIS’ largest city of Mosul, the Kurdish YPG today announced that they have begun such an invasion to “liberate” the city.

It is unclear what, if anything, is actually being done on the ground to that end yet, as the announcement simply came at a press conference, and all of the comments that followed were about things that would happen in the future, with the YPG emphasizing the offensive would happen with heavy US air support.

Some 30,000 members of the YPG-dominated group which styles itself as the Syrian Democratic Forces are to surround the city, with Defense Secretary Ash Carter saying the goal is to “isolate” the ISIS capital, and then start trying to enter the city itself.

The Mosul operation, already almost three weeks old, is expected to last multiple months, and early comments from officials suggest they believe Raqqa will be an even bigger and longer offensive. Kurdish officials also say they believe taking the city would effectively mean the end of ISIS in Syria.

While Iraq is already making specious arguments that Mosul will mean the end to ISIS in Iraq, the claim in Syria is even more outlandish, since ISIS still controls substantial territory above and beyond their capital city, including the majority of the Deir Ezzor Province. While the loss of Raqqa, if indeed they lose it to Kurdish forces, would be a major blow to ISIS, the group seems to be positioned to survive over the long run, even if it ultimately means going back to a landless insurgency.

The Kurdish offensive on Raqqa is likely to also fuel more anger from Turkey, which has repeatedly warned the US not to allow any Kurds in Raqqa. The US has talked up negotiating some joint operation, but the Kurds have similarly warned the US that Turkey can’t play a role in the battle. Turkey has overtly attacked YPG forces during anti-ISIS operations in recent weeks, and that could quickly derail the Raqqa operation.