With an offensive underway to take back Mosul from ISIS, Hillary Clinton called for the next step during the presidential debate: regaining Raqqa.
Taking back the Syrian city -- one of the first captured by ISIS -- would represent a major victory for the U.S. coalition. Raqqa now functions as the group's de facto capitol in Syria and could serve as a safe haven for ISIS leaders escaping from Mosul.
Back in March, the chief of U.S. Central Command said the U.S. had a plan to "isolate" Raqqa but not to "retake it."
First Mosul, then Raqqa?
It's been reported the U.S. is now working with its Arab partners on a plan for an assault on Raqqa.
The Wall Street Journal reports: "Such an operation would aim to isolate the extremists in the Syrian city, limit their ability to reinforce its satellite strongholds across Iraq and Syria and seal off escape routes."
Taking back Mosul from ISIS is one thing.
Regaining ISIS's headquarters in Syria would be an entirely different beast. Unlike in Iraq, where the government of Prime Minister Haider al-Abadi provides the U.S. with logistical support, the U.S. is limited by a lack of allies to coordinate with in Syria.
The U.S. doesn't work with Syrian government forces, which it's accused of war crimes for targeting civilians. Instead, the main U.S. partner on the ground in Syria is a Kurdish fighting force called the YPG, which makes up the bulk of an Arab coalition called the Syrian Democratic Forces, or SDF.
The Kurds are demanding they be armed by the U.S. in exchange for leading the battle against Raqqa. That's out of the question for Turkey, which considers the Syrian Kurdish forces an extension of a domestic rebel group it has been fighting for decades.
The political conditions are not right and the military force that we have to retake these cities is complicated at best.
Even if the U.S. could force ISIS out of Raqqa, finding and vetting local leaders to govern it would be its own challenge.
The Associated Press contributed to this report.