Iraqi Prime Minister Haider al-Abbadi has "retired"  the army's chief of staff, the most senior officer removed since rebel fighters  overran large parts of the country last year, his spokesman has said.

General Babaker Zebari "has been retired" on Abbadi's orders, Saad  al-Hadithi told the AFP news agency on Monday, without providing further details.

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Military sources say a Kurdish general with the Iraqi Air Force, Anwar Hamad Amin, is expected to replace Zebari.

Al Jazeera correspondent Jane Arraf, reporting from Baghdad, said that Zebari has been in the job for almost a decade now.

"He had asked himself to retire, that request has been refused several times. He was someone who was due to leave the job," she said.

"His replacement is said to be also a Kurdish general. This is essentially a policy position that has traditionally been given to Kurds."

Responsibility for the failure

Abbadi has sacked dozens of army and police officers in an effort to restructure and improve security forces that performed disastrously when the Islamic State of Iraq and the Levant (ISIL) group launched an offensive last June, overrunning major areas north and west of Baghdad.

Multiple Iraqi army divisions collapsed during the initial ISIL offensive, with soldiers abandoning weapons, vehicles and uniforms in their haste to flee.

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"Prime Minister Abbadi does really have a lot to answer militarily, and people are looking for some generals and other military officials to take responsibility for the failure of Iraqi forces in Mosul and Ramadi when they retreated," the Al Jazeera correspondent said.

"But this particular position is not seen as having had huge amount of bearing on those failures on the ground.

"What is now being acknowledged even that at the level of the prime minister is that there have been very very serious failures," she said.

Lacking leadership

The Iraqi military suffers from both poor training - which the US military says it largely abandoned after the 2011 withdrawal of American forces - and lacking leadership.

Zebari repeatedly said before the withdrawal that it would be better if US forces stayed, as it would take years for the Iraqi army to be fully ready.

"If I were asked about the withdrawal, I would say to politicians: the US army must stay until the Iraqi army is fully ready in 2020," Zebari had told AFP in 2010.

While Zebari was chief of staff, military responsibility was devolved elsewhere post 2011, with former Prime Minister Nouri al-Maliki centralising control of the armed forces in his office and bypassing the defence ministry.

Three and a half years after US forces left, there are thousands of American soldiers back in Iraq advising and training Baghdad's forces, and the US is leading a campaign of air strikes targeting ISIL in Iraq and Syria.

Source: Al Jazeera and agencies