In President Trump's 2018 State of the Union Address, he mentioned that the U.S. military captured Abu Bakr al-Baghdadi but released him. This may have been a surprise to many watching.
"We have foolishly released hundreds and hundreds of dangerous terrorists, only to meet them again on the battlefield — including the ISIS leader, al-Baghdadi," Trump said.
The U.S. did capture Baghdadi in February 2004, in the early days of the Iraq War. He was held at Camp Bucca, a prison facility in Garma, Iraq, along the country's border with Kuwait.
But back then he was just Ibrahim Awad Ibrahim Al Badry, a civilian detainee. He was one of some 80,000 detainees who were held at one of four detention facilities throughout Iraq. They were a mix of petty criminals and insurgents captured in house raids over the course of the war.
Baghdadi was captured in a house raid near Fallujah in 2004; he was described by U.S. officials as a "street thug" at the time.
Nine U.S. military review boards worked six days a week reviewing the detainees' cases over the lifetime of the prison system, resulting in 20-45 percent of captured prisoners being released.
The man who would become the Islamic State's caliph was held from February to December of 2004. But the U.S. didn't simply release him, they transferred him to the Iraqi justice system.
It was the Iraqi government who released Baghdadi.
Eventually, the 2008 U.S. Status of Forces Agreement with Iraq would set the terms for closing the prison system and moving the detainees to Iraqi custody. The American government was primarily concerned with some 200 prisoners they deemed most dangerous.
Baghdadi was not one of them.
At the time of his release, Baghdadi and the others who were released were considered "low level" and not much of a threat. After his release, he gravitated to the insurgent group led by Abu Musab al-Zarqawi, which came to be known as Al-Qaeda in Iraq.
Zarqawi was killed by U.S. forces in 2006. The Americans continued to systematically eliminate AQI's leadership. In 2010, Baghdadi was promoted to a leadership position in what was left of the network.
No one really knows how Baghdadi rose in the ranks. When his name was revealed as one of the group's leaders (which then started calling itself the Islamic State of Iraq), no one in U.S. intelligence knew any of their names. The seeds of what would become ISIS were sown.