There are also concerns about thousands of IS families — including Australian women and children — held in neighbouring Syria.
Tens of thousands of fighters’ family members remain in camps, with foreign governments, including Australia’s, reluctant to take their citizens back.
A recent military offensive by Turkey against their Kurdish captors, and the withdrawal of aid groups because of coronavirus, have made it more difficult to maintain these centres.
That has raised fears Islamic State may be able to bolster its numbers by staging mass breakouts, a tactic it previously used in Iraq.
Preventing the group from holding territory is critically important in stopping the Islamic State from becoming a global threat again, according to Michael Knights.
“If they are ignored, eventually Islamic State will regain the ability first to bomb Iraqi cities, and later to draw in volunteers from Western countries, and then to send them back again as attack operatives,” he said.
“If we want to prevent that from happening again, then we need to prevent the Islamic State from controlling even the smallest territories in Iraq and Syria.”