It has long been clear that Curveball – the Iraqi defector who provided much of the basis for the US government’s claims about the existence of weapons of mass destruction in the run-up to the Iraq war in 2003 – was a liar. But he has now finally admitted that he made up his claims about mobile bioweapons laboratories, which US Secretary of State Colin Powell used as a justification of invading Iraq in his famous presentation at the United Nations Security Council in February 2003. Curveball, whose real name is Rafid Ahmed Alwan, had until now refused to speak to the press. But in an interview with the Guardian earlier this month in Karlsruhe in Germany, where he now lives, he said that he lied in order to help topple the regime of Saddam Hussein. “I and my sons are proud of that and we are proud that we were the reason to give Iraq the margin of democracy”, he said. Obviously, this was a huge cock-up with disastrous consequences. The question is: whose fault was it?

According to Joschka Fischer, who was Germany’s foreign minister at the time of the Iraq war, the United States was clearly to blame for inflating the importance of Curveball, who was a German rather than US intelligence source. In response to a question from the Guardian‘s Berlin correspondent at the launch of the second volume of his memoirs earlier this month, he said that Germany – which opposed the Iraq war – had shared its doubts about Curveball with the US. “Our position was always: [Curveball] might be right, but he might not be right. He could be a liar but he could be telling the truth,” he said. In the book, he says Germany faced a difficult dilemma. “On the one hand we couldn’t and didn’t want to withhold from our NATO partner any relevant information we had about possible WMD in Iraq,” he writes. “On the other hand, we did not want to take part in any propagandistic exploitation of unproven material and thereby encourage a war.” The German “security cabinet” (which included Fischer) therefore decided that the German foreign intelligence service, the BND, should give US intelligence agencies “all the information we had, albeit together with our assessment that these were the claims of a deserter that could not be substantiated or verified that could be right or could be completely wrong.”

This account suggests that the German government and intelligence services were perfectly open with their US counterparts. In fact, however, part of the problem was that the BND consistently refused to allow the Defence Intelligence Agency (DIA) or the CIA direct access to Curveball. According to former Los Angeles Times reporter Bob Drogin’s book, this was partly because, when Curveball first talked to BND, he told them that Saddam was using German-manufactured equipment to develop biological weapons. Ernst Uhrlau, then Chancellor Schröder’s director of intelligence and now head of the BND, panicked because of the previous involvement of German companies in chemical weapons production in Libya (which the German media had dubbed “Auschwitz in the sand”) and Iraq in the 1990s. Curveball’s BND handler, who resented US intelligence, told his bosses that Curveball was anti-American and therefore would not talk to US intelligence agencies, which gave them an excuse to refuse the DIA’s request to interview Curveball in 2000. Although the BND played down Curveball’s significance somewhat in 2002 (although Tyler Drumheller, the head of the CIA in Europe, worried that this might be because the Schröder government was by then publicly opposed to the war, regardless of the existence or otherwise of WMD), it never actually admitted Curveball wasn’t credible (and in fact continued to pay him until 2008). According to Drogin, when US intelligence agents finally got access to Curveball after the war, they thought it was obvious he was a fabricator.

The story of Curveball is therefore a complex one involving errors on both the US and the German side and the law of unintended consequences. Clearly, the main problem was that parts of the Bush administration wanted to invade Iraq regardless of the evidence of WMD and was prepared to distort intelligence in order to make the case for war. But the role of the German government and intelligence services complicated things. As Fischer suggests, the Germans worried that sharing Curveball with the Americans might actually strengthen the case for war (which, incidentally, also illustrates that German intelligence didn’t think his claims were completely implausible). What in fact happened, however, was that because the CIA and the DIA did not have direct access to him, they were unable to see for themselves just how weak his claims were. It’s impossible to know what would have happened if they had been able to interview Curveball earlier and had seen through his lies. But it seems to me that if the Germans had been more co-operative, it might just have made the Iraq war slightly less – not more – likely.