Ten years ago this week, the U.S. invaded Iraq, citing intelligence that turned out to be bogus. I had to work on some of it – and I also had to work on keeping the really, really terrible versions of it out of our analysis.

Specifically, I was a CIA analyst working in the Counterterrorism Center in the overburdened days after 9/11. As analysts, we spend most of our time identifying burgeoning issues based on communications intercepts, reports from CIA case officers, imagery from satellites, accounts from other governments, and piecing together a story.

What we don't do routinely is tie one catastrophe to another. But that was exactly what I was asked to do in November 2002, shortly after Congress voted to authorize war with Iraq. That war was predicated on Saddam Hussein's (ultimately nonexistent) stockpiles of deadly weapons, but lurking in the background was the assertion that he'd pass them on to al-Qaida. At the CIA's Iraq Branch in the Counterterrorism Center, we didn't think Saddam had any substantial ties to al-Qaida. But soon we found ourselves fielding questions from determined Bush administration officials about whether Saddam was tied to 9/11.

That's how my team ended up in a windowless room with my branch chief, "Karen," who was pretending to be Dick Cheney or his chief of staff, Scooter Libby.

That month, Vice President Cheney scheduled a meeting with our Branch to discuss our assessment of Iraq's relationship with al-Qaida and 9/11. It was his second visit to the Branch; there always seemed to be more questions. The Branch Chief called us together for a practice session in a bland conference room a few days before their arrival. At this so-called "murderboard" session, we weren't stripping down our analysis to find data we'd missed. We were practicing how to defend our perspective when questioned by the Vice President of the United States.

The Branch Chief would get the ball rolling with questions designed to lead us down a rabbit hole. Karen had briefed Libby, so she was skilled at impersonating both the Vice President and Libby – that is, she was being relentless and insistent – to anticipate the questions they would ask. We had a bottom line: Fear of Islamic extremism growing in Iraq would limit Saddam's willingness to work with bin Laden. Fake-Cheney would rejoinder: Would ideological differences really hinder their cooperation? Anticipating the response, she'd come back with: What if bin Laden convinced Saddam that acting against the United States was in both of their best interests; you have told us we don't know exactly how much communication has taken place between the regime and al-Qaida; and you have already found information that specified safe havens, contact and training?

We needed to poke holes in our analysis, to be sure we were right. If not, we could rest assured Cheney would. Already, Cheney's Pentagon ally, Undersecretary of Defense Doug Feith, had put together an alternative analysis faulting our own and asserting instead that "multiple areas of cooperation" existed between al-Qaida and Saddam. The ongoing questions and briefings became a labyrinth.

How far down a rabbit hole should we go in answering questions? Will it be misconstrued as an actual answer based on a made-up scenario? It was an unorthodox practice. But we were unused to a senior political figure being willing to dig down into the details of our analysis.

In the abstract, challenging CIA's analysis is a good thing: agency analysts get stuff wrong, as evidenced by Saddam's non-WMD. But in this case, it was problematic. The nature of intelligence analysis is to gather as much information as possible to assist a policymaker in making difficult choices. If a policymaker has a preference for what the intelligence product should say, that pollutes the objectivity of the intelligence – and diminishes its value.

On Sunday, March 16, 2003, I watched Cheney on "Meet The Press" contradict our assessment publicly. "We know that he [Saddam] has a long-standing relationship with various terrorist groups," Cheney said, "including the al-Qaeda organization." I was basically watching Cheney field-test arguments that we would have to anticipate – and rebut – at CIA. Except instead of asking us questions behind closed doors, Cheney was asserting to the public as fact something that we found to be anything but. I found myself yelling at the TV like I was contesting a ref's blown call in a football game.

The agency's intelligence collection on Iraq's relationship with al-Qaida was thin – Iraq's connections to terrorist organizations were so minute it wasn't a priority for us – so it was difficult to even construct a chart showing connections, as if we were mapping the Barksdale crew on The Wire. Saddam has a history of supporting small, anti-Israel terrorist groups; in early 2002, due to the war in Afghanistan, the terrorist leader Abu Mus'ab al-Zarqawi moved into Iraq on his own, with no direction or control by al-Qaida or Saddam; there were reports of varying reliability saying Iraq had discussions with al-Qaida about establishing a safe haven, dating from the early 1990s. The Zarqawi stuff would prove to be relevant, after the U.S. invasion. The rest of it didn't add up to much. We concluded that, at most, the relationship between Iraq and al-Qaida was like two independent groups trying to exploit each other.

None of that stopped the invasion. Nor did the invasion stop the troll-y back-and-forth with the White House on Saddam and terrorism. When I volunteered to deploy to Iraq, my boss' boss wouldn’t spare me for four days' worth of weapons training. ( "I would rather have you come back in a body bag than spend that much time out of the office," he told me.) They were so frantic to respond to White House questions that supporting the actual war effort took a back seat.

As it turned out, the questions wouldn't stop once the invasion occurred. In June 2003, the Defense Department started to report that troops discovered caches of Iraqi Intelligence Service (IIS) documents allegedly proving Saddam was tight with al-Qaida.

The documents claimed to directly link Mohammed Atta, one of the main 9/11 hijackers, with the Baghdad training camp of Abu Nidal, the infamous Palestinian terrorist. It was a hand-written note, supposedly by Tahir Jalil Habbush al-Tikriti, the former head of the Iraqi Intelligence Service (IIS). If the documents were real, it was damning evidence that Iraq worked with al-Qaida long before the 9/11 attacks; if not, someone embarked on a very sophisticated strategy to play the U.S. government, our team or both.

And if this was truly a smoking gun, our team would be blamed – rightly – for getting it wrong. There was a sense of urgency at the CIA to evaluate these documents and provide an answer.

We got to work. We worked with the Secret Service to test the ink. If we could determine how old the ink itself was, we would have a time frame for when the documents were prepared. While in Iraq, I asked every high-level Iraqi government detainee I could about the details of the document. They either had grave doubts, or flatly said the document was bogus. They were adamant the names and roles outlined in the documents didn't match the structure of the IIS. Having studied the Iraqi intelligence apparatus extensively before the war, everything they said lined up with the structure we understood to be true. The FBI had put together a timeline of Atta's 2001 travels around the world, culling together airline records, ATM withdrawals and hotel receipts. Much like the infamous "Prague meeting" – another ultimately-bogus thread weaving al-Qaida together with Saddam – the FBI material indicated Atta was in the U.S. when the IIS document indicated he was meeting with Abu Nidal in Iraq.

Our Branch Chief, Karen, walked into Cheney's office with everything we'd uncovered about the Abu Nidal link in June 2003. It seemed airtight. The Secret Service had determined that the paper was made after the date printed on the page. The timeframes didn’t match. The ink was inconsistent with the ink manufactured in the early 1990s purported timeframe of the documents. The chain of command indicated in the documents contradicted the description of the Iraqi intelligence bureaucracy provided by our detainees, even down to incorrect titles. These were forgeries.

I wasn't there, but I heard the vice president was gracious and thanked her.

I actually quit the CIA for 3 days in 2004. I was exhausted answering historical questions trying to justify the invasion while at the same time trying to define Iraqi al-Qaida leader Zarqawi's growing role as a real threat. I couldn't take it. People were dying and we were still talking about evidence of a connection between Saddam and al-Qaida. After a few phone calls with leadership in the Counterterrorism Center, I went back after 3 days and switched roles to the operations side – the National Clandestine Service – heading up the targeting operations team looking for Zarqawi. Instead of writing about him, I wanted to find him, I felt like the U.S. accidentally gave him a platform that helped him grow into a major terrorist. I moved onto another assignment a few months before he was killed in 2006.

After leaving the CIA, I've had a lot of time to reflect on this sorry absurd role in intelligence history, and my bit role in it. No intelligence analyst should have to deal with policymakers delving into intelligence work. It sounds bureaucratic and boring, but the distinction matters: CIA doesn’t have a policy agenda, it seeks to inform those agendas. Politicians and appointees have ideas for shaping the world. Mingling the two is a recipe for self-delusion and, as we saw in Iraq, failure.