How did the United States of America launch a war against Iraq?

On March 19, 2003, the United States launched one war against Iraq which was under the code name ‘Operation Iraqi Freedom’ which was to be joined by forty different nations under the leadership of the United States on the ground in order to prevent Iraq from producing weapons of mass destruction with no evidence accessible against Iraq. Thus, the ostensible purposes were dissimilar as monitoring Iraqi Oilfields in addition to installing a regime that is friendly to the United States.