The Australian Defence Force (ADF) will now have the power to target Islamic State (IS) logistics and support personnel, Prime Minister Malcolm Turnbull announced on Thursday.

Previously, the ADF was only permitted to target IS combat fighters.

“Under international law, all members of an organised armed group such as Daesh (IS) can be targeted with lethal force, subject, of course, to the ordinary rules of international humanitarian law,” Mr Turnbull told Parliament on Thursday.

“This is a reasonable and conventional approach adopted by the armed forces of our key allies across the world.”

The PM said previous restrictions had prevented the ADF from operating as freely as their foreign counterparts, and were at risk of being prosecuted if they did target IS support personnel.

Professor Peter Leahy, director of the National Security Institute at the University of Canberra, said the new powers would simply let the ADF target the IS bomb makers, not just bombers.

The status of IS

On August 29, IS announced its second-in-command and chief spokesperson, Abu Muhammad al-Adnani, had been killed in the IS-held city of Aleppo, Syria.

It was a significant blow for the group; Adnani was often seen as the face of IS and only in May had publicly encouraged terror attacks on America and Europe.

The death of Adnani came as the militant group continued to lose ground, and as US-backed Syrian and Turkish forces unite.

On Thursday, Sydney man Hamdi Alqudsi was sentenced to at least six years’ jail for recruiting Australians to fight for IS in Syria.

In July, research firm IHS reported IS had shrunk from 90,800 square kilometres to 68,000 – amounting to a loss the size of Ireland.

Abu Mohammed al-Adnani died, presumably from wounds, this week. Photo: AAP

Dr Rodger Shanahan, research fellow at the Lowy Institute for International Policy, said IS had been shrinking for a long while.

“It still retains an ability to fight defensively but has shown very limited ability to manoeuvre offensively for some time now,” he said.

A ‘sensible update’

Professor Leahy, who also served as chief of the Australian army from 2002 to 2008, wholeheartedly supported the broadening of ADF powers.

“This is something that would have been useful to have had earlier,” he said, suggesting that the legal process of lifting the restriction had likely delayed the change.

Islamic State still holds the Syrian city of Aleppo. Photo: AAP

He said until now, Australian military had been allowed to target IS bombers but “not the bomb makers”.

Dr Shanahan said the ADF may be feeling the impact of the restriction more now that there were less moving targets.

“There may be fewer ‘dynamic’ targets that fall within our ROE [rules of engagement] and more static targets that we haven’t been able to prosecute in the past,” he said.

The threat of prosecution

In his speech to Parliament, Mr Turnbull did not suggest that the ADF had been threatened with prosecution.

But Professor Leahy said that, hypothetically, an Iraqi person with relatives in Australia could have attempted to bring a case against the ADF – until now.

Professor Peter Leahy served as chief of the Australian Army from 2002–2008. Photo: AAP

“There definitely could have been groups here in Australia trying to make a move on it,” he said.

Professor Leahy argued that although IS was losing ground, the war was not only being fought geographically, but ideologically.

“We might get the territory back but we’re not going to defeat the radical Islamist ideologically that quickly,” he said.

In his paper, ‘Another Century, Another War’, Professor Leahy predicted the war against terrorism would last for the rest of this century and beyond.