- Islamic State fighters inside Mosul will be heavily outnumbered by Iraqi security forces and will rely on a network of tunnels to launch suicide IED attacks and potentially a chemical weapons attack in defending the militant group's hold on the city.
- IHS Markit assesses that the Islamic State is unlikely to engage in a long and protracted battle for the defence of Mosul that would deplete what remains of its resources; a quicker operation taking a few weeks is likely if the bulk of the militant Islamist fighters retreat for Syria and/or the remaining fighters show an unwillingness to fight amid low morale and emboldened local resistance to its presence.
- It is very probable, however, that a guerrilla insurgency will be mounted in earnest once the operation is over, using its support networks in the city's western neighbourhoods and suburbs.
Iraqi Special Operations Forces near Mosul, Nineveh province, said on 20 October that they were 7 kilometres from the Islamic State-held city.
Indicators likely to determine the duration of the battle for Mosul include the number of Islamic State fighters who attempt to leave the city for Syria. According to a report by Russia's Ria Novosti news agency in the week prior to the operation's launch on 17 October, Islamic State fighters were being encouraged to leave Mosul for Syria through a safe passage that would reportedly be left open on the western side of the city. On 13 October, social media reports emerged of a convoy of Islamic State militants and their families from Mosul arriving in Raqqa, Syria. The Syrian Observatory for Human Rights additionally claimed on 17 October that Islamic State was reorganising the Islamic Police (Hisba) in Raqqa in order to absorb the influx of Iraqi fighters. In July 2016, Iraqi news reports had also alleged that 1,500 Islamic State members, including senior leaders, had fled to Syria soon after the recapture of Qayyarah air base.
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