A talented soccer player. A keen scholar with a PhD from Baghdad University. This is how the head of the brutal militant organisation Islamic State terrorist group has been described.

On Tuesday, Australia’s Defence Minister Kevin Andrews failed to name the group’s leader, Abu Bakr al-Baghdadi, in an interview on ABC television.

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Appearing on 7.30 on Tuesday night, Mr Andrews declined to name the 43-year-old because of “operational matters”, but there is plenty of information on the militant leader already in the public sphere.

Abu Bakr al-Baghdadi is the world’s second most wanted terrorist by the US government, with a $10 million reward for information leading to his capture.

Only the leader of al-Qaeda, the organisation behind the 9/11 attacks, merits a larger reward of $25 million.

Abu Bakr al-Baghdadi making a rare appearance in 2014. Photo: AAP

According to a report by The Daily Telegraph, Al-Baghdadi was a “polite, bespectacled student” who shone on the football field, earning the reputation as the best soccer player for a local team.

He apparently lived in a small room attached to a mosque for more than a decade as he completed his masters, and then his doctorate in Islamic studies.

There are conflicting reports about whether al-Baghdadi was focused on his young family or involved in terrorist activity at the time of the American invasion of Iraq in 2003.

According to the BBC, he helped to found the militant group Jamaat Jaysh Ahl al-Sunnah wa-l-Jamaah after the invasion, and was later imprisoned in Camp Bucca, a US facility in Iraq.

Al-Baghdadi during his US detention.

He was detained for several years and, once released, went on to become a high-level commander of al-Qaeda in Iraq, also known as the Islamic State of Iraq.

As Syria descended into civil war, al-Baghdadi began sending his men over the border, and in April 2013, he announced the creation of ISIL (Islamic State of Iraq and the Levant).

Local jihadist faction Jabhat al-Nusra and al-Qaeda told al-Baghdadi to withdraw, but he defied both groups, and took control of a reported 80 per cent of Jabhat al-Nusra’s fighters.

By June 2014, al-Baghdadi declared the establishment of a worldwide caliphate and named himself the leader of Muslims around the world.

He remains reclusive and is hardly seen even amongst his own men, earning himself the nickname “the invisible sheikh”.

Local media reports claim al-Baghdadi fled Syria in October after being seriously injured by violent coalition airstrikes.

In January, Iraqi Prime Minister Haidar al-Abadi said the ISIL leader had been injured by another airstrike in an Iraqi border town, calling it “a miracle” he survived.

He remains in hiding and his current location is unknown.