Since Iraqi troops seized back Mosul last month, the self-proclaimed Islamic State has been reduced to the area around Raqqa in Syria. Predominantly Kurdish forces are attempting to take the city, protected by Western airpower. Authorities estimate the number of Islamist fighters has dwindled from the thousands to the hundreds.

As soon as the caliphate falls, governments will face another challenge: the reconstruction.

Repairs to basic infrastructure in Mosul alone could cost up to $1 billion, according to the United Nations.

Iraq’s Ministry of Planning puts the long-term cost of rebuilding Mosul at $10 billion. That includes repairing the damage from the fighting as well as the deliberate destruction caused by the Islamic State.

Given Iraq’s history of corruption and mismanagement of public funds, the final figure could be much higher. And that’s just Mosul.

Western countries cannot relax security spending either. Foreign fighters will return home to Europe while the caliphate’s last stand could inspire sympathizers in the West to commit more terrorist attacks, similar to the ones on Thursday.