Bolton has long been one of the most hawkish of all the neoconservative hawks. He was part of the Bush-Cheney crew that claimed Saddam Hussein had amassed weapons of mass destruction and that war was the only option. As a top State Department official prior to the 2003 Iraq invasion, Bolton pushed the false claims that Iraq had obtained aluminum tubes and uranium for its supposed nuclear weapons program. He was also a supporter of a conspiracy theorist named Laurie Mylroie who contended that Saddam was behind the 9/11 attacks. Before Bush launched the Iraq War, Bolton predicted that "the American role actually will be fairly minimal." (In 1997, he was one of several conservatives who wrote to President Bill Clinton and urged him to attack Saddam.)
Not surprisingly, Bolton has stuck to the position that the Iraq invasion was the right move. In May, he said, "I still think the decision to overthrow Saddam was correct."
http://www.motherjones.com/politics/2015/08/donald-trump-john-bolton-iraq-war