According to the WorldNet Lexical Database, a cakewalk is "a strutting dance based on a march; was performed in minstrel shows; originated as a competition among Black dancers to win a cake....an easy accomplishment; 'winning the tournament was a cakewalk for him'; 'invading Iraq won't be a cakewalk'". 
In February 2002, Kenneth Adelman, an assistant to Donald Rumsfeld in the 1970s and now a leading neoconservative defense intellectual, wrote, "demolishing Hussein's military power and liberating Iraq would be a cakewalk." He predicted that Saddam Hussein would quickly fall if the US military attacked his 'headquarters, communications, air defenses and fixed military facilities through precision bombing.' ..."
Opposing views weren't well received until it was too late.
Adelman posted a triumphalist op-ed in the April 10, 2003 Washington Post entitled "'Cakewalk' Revisited": http://www.drumbeat.mlaterz.net/Op-Ed/Ken%20Adelman%20'Cakewalk'%20Revisited%20041003a.htm
On May 14, 2004, Deputy Secretary of Defense Paul Wolfowitz claimed that, in response to recent difficulties in the occupation of Iraq, "no one should have expected a cakewalk and that's no reason to go wobbly now." http://www.nytimes.com/2004/05/16/weekinreview/16tier.html&OQ=8hpib