Terrorist behind takedown of Mosul in Iraq was released by Obama in 09

http://www.telegraph.co.uk/news/worldnews/middleeast/iraq/10891700/Iraq-crisis-the-jihadist-behind-the-takeover-of-Mosul-and-how-America-let-him-go.html

Obama's own words:

I will stand with the Muslims.

Abu Bakr al-Baghdadi was being held at Camp Bucca which was closed because of a 2008 security pact between the US and Iraqi government.
Under this pact, prisoners and detention camps were handed over to the Iraqi government.

http://foxnewsinsider.com/2014/06/13/next-bin-laden-isis-leader-abu-bakr-al-baghdadi

The US wanted him to remain a detainee, but the Iraqi government released him.