The FBI that failed on 9/11 is the creation and captive of its spectacular and controversial past. Its original mission -- the investigation and prosecution of only the most serious crimes against the United States -- was forsaken almost from the beginning. This abandonment of purpose has been accompanied by a long history of political pressure, both from within and without. This sorry and scandal-ridden path culminated in a twenty-five-year run-up to 9/11 in which predictable and preventable lapses became hopelessly entrenched.

In Broken, Richard Gid Powers, one of the country's...