The military released 77,000 of about 87,000 detainees locked up during the Iraq war because there was not enough evidence to hold them, CNN has learned. In most cases, if we do n't have anything, eventually they 'll be released, said Brig. Gen. David Quantock, who oversees detainee operations in Iraq. Quantock said many cases are driven purely on intelligence. Intelligence does not win a fight in a courtroom. It does n't win the fight in a courtroom in the United States. It does n't win in Iraq. According to the U.S. military, 76,985 detainees have been released out of the 87,011 captured during the Iraq war. A CNN investigation found that frustration over the Army's policy on detainees may have led to the 2007 killings of four Iraqi men by three decorated Army sergeants at a Baghdad canal. Former 1st Sgt. John Hatley, who led the mission that day, told CNN in a letter that the detainee policy has extensive flaws that repeatedly frustrated soldiers. On Army interrogation tapes obtained by CNN, other soldiers complained about the Army rules for evidence gathering. Despite the high release rate, Quantock said he has confidence soldiers can take basic evidence from a crime scene in Iraq. We 're asking them to take basic evidence, which they 've been trained to do, said Quantock, who oversees detainee operations in Iraq. We 've got the greatest soldiers in the world. And I