It has now been more than two decades since Secretary of State Colin Powell briefed the United Nations on America’s case for preemptive war on Iraq. “These are not assertions. What we’re giving you are facts and conclusions based on solid intelligence,” he declared.

Powell did not knowingly mislead. But how did the intelligence community get Iraq’s weapons of mass destruction so wrong? The scandal was huge, even more so since the Bush administration made WMD its prime public rationale, even though many other factors contributed to President George W. Bush’s decision to go to war.