America and its allies will break Isil's grip on the vital strongholds of Raqqa in Syria and Mosul in Iraq "within months", the US defence secretary said yesterday (Thursday).
The two cities are the most significant population centres still in the hands of Islamic State of Iraq and the Levant. Raqqa is the movement's de facto capital; Mosul is the biggest conurbation under its flag and where Abu Bakr al-Baghdadi proclaimed the birth of "Islamic State" in 2014.
Retaking the cities is the US-led coalition's main objective. Their fall would deal a severe blow to Isil, calling into question its ability to rule territory.
Ashton Carter, the US defence secretary, told the BBC that Isil's control over the two cities would be broken "within months". He said: "Our plan calls for the envelopment - that is the surrounding and the collapsing of Isil's control - over these two key cities, Mosul and Raqqa, and that envelopment is under way now."
Already, the Iraqi army, Shia militias and Kurdish Peshmerga forces have come close to isolating Mosul and severing its links with Isil-held territory in neighbouring Syria. Meanwhile, the Syrian Democratic Forces (SDF), a Kurdish-led alliance of armed groups, has advanced to within 30 miles of Raqqa. US and coalition air strikes are targeting Isil command centres and military sites in both cities.
A delay has been imposed by the need to assemble ground forces.
America and its allies are also trying to ensure that Iraq's national army - not Shia militias - take Mosul and want to strengthen the Arab component of the SDF before trying to capture Raqqa.
The assault on Mosul will probably take place first because Iraq's army has already advanced towards the southern approaches. The retake of Raqqa may take longer, complicated by Turkey's anxiety to ensure the Kurdish-led SDF does not take more ground.