As the initial elation over the swift identification and ending of the Brothers Tsarnaev manhunt fades, a steady stream of facts are emerging that strongly suggest the need for a more sober assessment of the FBI's performance in the two years prior to the Boston Marathon bombing.

FBI counter-terrorism agents interviewed Tamerlan Tsarnaev, the older of the brothers, in January 2011 after receiving a tip from Russian intelligence. Since the interviewing agents thought they heard nothing to indicate Tsarnaev was a terrorist, little else was done and the case was closed two months later. A few months after that, Tsarnaev went to Russia and encountered somebody or experienced something that apparently prompted him to become quite open about his devotion to a radical vision of Islamic jihad. The FBI visited him a second time after he returned to the United States but again concluded that Tsarnaev was not a threat. It is speculation now, of course, but it's difficult to believe the Tsarnaevs would have been able to carry out the bombing had they been under active surveillance before the 2013 Boston Marathon.

Whatever else may yet be discovered about what the FBI missed, there is no excuse for the agency not grasping the significance of the radical Islamist video Tamerlan posted on his Facebook page entitled "The Emergence of Prophecy: The Black Flags of Khorasan." The video explains and glorifies the prophecy of a mighty Jihadist army rising from the Iranian region of the Near East to conquer the world and establish an enduring Muslim empire. The Khorasan connection is a staple of al Qaeda ideology, and the video's presence on Tsarnaev's Facebook page was a red flag that should have alerted agents to a very real potential danger.

It is quite possible, though, the FBI agents who interviewed Tsarnaev on both occasions failed to understand what they saw and heard because that's what they were trained to do. As The Washington Examiner's Mark Flatten reported last year, FBI training manuals were systematically purged in 2011 of all references to Islam that were judged offensive by a specially created five-member panel. Three of the panel members were Muslim advocates from outside the FBI, which still refuses to make public their identities. Nearly 900 pages were removed from the manuals as a result of that review. Several congressmen were allowed to review the removed materials in 2012, on condition that they not disclose what they read to their staffs, the media, or the general public.

With the recent proliferation of revelations about FBI blindness on the Brothers Tsarnaev, a comment made last year by Rep. Louie Gohmert, R-Texas, to Flatten now has a tragic resonance: "We've got material being removed more because of political correctness than in the interest of truth and properly educated justice officials. We are blinding our enforcement officers from the ability to see who the enemy actually is." The Boston bombing showed the tragic consequences of that blindness.