Vulliamy closely covered the lead-up to the invasion of, and war in, Iraq from 2002 onwards. He clashed with his newspaper, "The Observer", over its support for the invasion, often unable to place his stories about false intelligence and non-existence of weapons of mass destruction in the paper (see "Official Secrets" film below, 2019). He reported from Iraq several times from early 2003 to 2005, on civilian casualties of the invasion, and on the subsequent insurgency.