Published: 10:55 EST, 13 June 2014 | Updated: 14:20 EST, 13 June 2014
The United States once had Islamic State of Iraq and al-Shams (ISIS) leader Abu Bakr al Baghdadi in custody at a detention facility in Iraq, but president Barack Obama let him go, it was revealed on Friday.
Al Baghdadi was among the prisoners released in 2009 from the U.S.'s now-closed Camp Bucca near Umm Qasr in Iraq.
But now five years later he is leading the army of ruthless extremists bearing down on Baghdad who want to turn the country into an Islamist state by blazing a bloody trail through towns and cities, executing Iraqi soldiers, beheading police officers and gunning down innocent civilians.
Scroll down for video
These are the only two known photos of Abu Bakr al-Baghdadi. He is seen here on the left as a prisoner half a decade ago and on the right more recently as the shadowy head of the Islamic State of Iraq and the Levant, ISIL, also known as ISIS
This uundated handout picture of jihadi leader of The Islamic State in Iraq and the Levant (ISIL), Abu Bakr al-Baghdadi, also known as Abu Du'a, was provided by the Department of State. The U.S. government has a $10 million bounty out for the al Qaeda leader
It is unclear why the U.S. let the merciless al Qaeda leader slip away, however, one theory proposed by The Telegraph is that al Baghadadi was granted amnesty along with thousands of other detainees because the U.S. was preparing to pull out of Iraq.
The United States began withdrawing troops from Iraq in 2010,and Camp Bucca closed in 2011 along with the United States' other military facilities as President Obama declared that the War in Iraq had come to an end.
Another possible explanation is that al Baghadadi did not become a jihadist until after his release from Camp Bucca.
The story of how Baghadadi ended up in U.S. custody in the first place and later came to be the leader of a violent terrorist group is the stuff of legend.
It is said by some that al Baghadadi was in the wrong place at the wrong time when he was picked up by the U.S. military, a farmer who got caught up in a massive sweep. It was at Camp Bucca that he was radicalized and became a follower of Osama Bin Laden.
Another version of the story is that al Baghadadi, who also goes by the alias of Abu Duaa, was an Islamic fundamentalist before the U.S. invaded Iraq and he became a leader in al Qaeda's network before he was arrested and detained by American forces in 2005.
'Abu Duaa was connected to the intimidation, torture and murder of local civilians in Qaim,' according to a 2005 U.S. intelligence report.
'He would kidnap individuals or entire families, accuse them, pronounce sentence and then publicly execute them.'
Crazed: Jihadists are carrying out summary executions on civilians, soldiers and police officers including this police major after taking control of large swathes of Iraq
Shock and awe: An ISIS propaganda video shows militants blindfolding a Sunni police major in his home before cutting off his head
Barbaric: This picture of the police officer's decapitated head resting on his legs was tweeted with the message: 'This is our ball. It is made of skin#WorldCup'
The U.S. now has a $10 million warrant out out of the brute, who is accused of bombing a mosque in Baghadad in 2011 and killing former Sunni lawmaker Khalid al-Fahdawl.
Al Baghadadi's use of aliases has made him a difficult man to pin down. The terrorist organizer rarely shows his face - even to his followers. There are only two known pictures of him in existence, and one is from before he was released from prison.
'We either arrested or killed a man of that name about half a dozen times, he is like a wraith who keeps reappearing, and I am not sure where fact and fiction meet,' Lieutenant-General Sir Graeme Lamb, a former British special forces commander, told The Telegraph.
'There are those who want to promote the idea that this man is invincible, when it may actually be several people using the same nom de guerre.'
Al Baghadadi and his troops had already taken key cities of Fallujah and Ramadi in Iraq earlier this year and have conquered the Iraqi cities of Tikrit and Mosul within the last several days.
They are now on the war path to Iraq's capitol city Baghadad.
The terrorist group's sudden rise in Iraq has taken the United States mostly by surprise.
President Obama famously said in October of 2011 that the American soldiers leaving Iraq would come home 'with their heads held high, proud of their success.
'That is how America’s military efforts in Iraq will end.'
Obama rules out sending troops back to Iraq
President Obama reiterated on Friday that, 'We will not be sending us troops back into combat in Iraq'
Faced with the real possibility that Iraq's capitol could fall into the hands of terrorists, President Obama is now rethinking America's military engagement in Iraq.
The president said on Thursday that he would consider launching air strikes on al Baghadadi and his followers.
'What we've seen over the last couple of days indicates Iraq’s going to need more help' from the United States and other nations, Obama said yesterday from the Oval Office.
'I don't rule out anything,' he said, 'because we do have a stake in making sure that these jihadists are not getting a permanent foothold in Iraq – or Syria, for that matter.'
In his daily briefing with reporters, White House Press Secretary Jay Carney clarified that president Obama was specifically referring to airstrikes.
'We're not considering boots on the ground,' he said.
Thousands of Iraqi soldiers, men and boys captured by ISIS
On the warpath to Baghdad: A graphic showing the town and cities captured by ISIS over the last few days
Up in arms: Members of Iraqi security forces chant slogans in Baghdad Sunni Islamist militants pressed towards the capital
Sabre-rattling: An Islamic militant issues a call to arms, saying: 'Declare Allah the Greatest! Allah is the Greatest!' in a video released by ISIS
President Obama reiterated on Friday that, 'We will not be sending us troops back into combat in Iraq.'
Obama said the U.S. would not get involved at all militarily until Iraqi President Nouri al-Maliki and other members of the government demonstrate that they can put aside their secretarian differences and work toward unifying the country.
'Ultimately it's up to Iraqis to solve their problems,' Obama said.
ISIS militants in Mosul stamp on Iraqi military uniforms
Volunteers who have joined the Iraqi Army to fight against the predominantly Sunni militants, who have taken over Mosul and other Northern provinces, gesture from an army truck
Kurdish Peshmerga forces seize the control of Kirkuk where Iraqi army forces and Islamic State of Iraq and the Levant clashed
The news that the U.S. may have played a role in the rise of the new Osama bin Laden comes just a week after President Obama released five Taliban commanders in exchange for a U.S. solider being held hostage by the terrorist network.
Lawmakers immediately questioned the logic of the president's decision, saying that the move could end up backfiring on the U.S. if the five fighters return to the battlefield in Afghanistan once their mandatory one-year stay in Qatar comes to a close.
They are especially concerned given the president's announcement just days before their release that he plans to withdraw the majority of America's troops in Afghanistan by the end of this year.
Already one, of the Taliban 5 have vowed to return to Afghanistan to fight American soldiers there once he is able.
'I wouldn't be doing it if I thought that it was contrary to American national security,' the president said at the time.