The military operation to wrest Mosul from ISIS could become the single largest, most complex humanitarian operation in the world in 2016, a UN official said Monday. Lise Grande, the UN humanitarian coordinator for Iraq, said that in the worst case scenario, some 1 million civilians could flee the city, with 700,000 of them requiring shelter—overwhelming emergency sites that currently only have the capacity to hold 60,000 people, the AP reports. It can't be done right now, and even in "the intermediate-term, if they couldn't go back to Mosul quickly, if there was too much damage in the city, then it would test us to the breaking point," Grande said.
"In the worst-case scenario, we can't rule out the possibility that there may be a chemical weapons attack," Grande said, warning that ISIS "may try and hold civilian populations either as human shields or forcibly expel huge numbers of civilians in the face of an attack by the Iraqi security forces knowing the Iraqi forces will not fire on their own people." The Guardian reports that American aircraft have started dropping millions of leaflets over Mosul, warning residents to stay in their homes, advising them on how to comfort children and avoid flying glass during bombings—and advising against trying to flee the city.