The Habbush Affair

In December 2003, a letter from Iraqi Director of National Intelligence Tahir Jalil Habbush al-Tikriti to Saddam Hussein dated in 2001 was "discovered" by the provisional regime in Baghdad. The letter "proved" that Iraq had WMD and had trained Muhammad Atta. 

Here (and here) is the initial Telegraph reporting on the discovery of the letter.

Ron Suskind's new book claims (based on interviews with CIA sources) that Habbush informed the CIA in 2001 that Iraq had no WMD the White House ordered the CIA to forge the letter to justify the war ex post facto. 

Amy Goodman and WaPo on Habbush  Affair.