The invasion of Iraq was in response to on-going violations of the CEASE FIRE AGREEMENT (there was NO formal Peace Treaty signed between the UN and Iraq after Iraq invaded Kuwait ... so that war never ended ... and Iraq was at great risk of the War resuming).
Review of History leading to invasion of Iraq:
(1) Iraq invades Kuwait to start the war !!!!!!!!!!!
(2) UN uses military force to throw Iraq out of Kuwait
(3) Iraq agrees to a ... CEASE FIRE ... to prevent an invasion of Iraq by the UN military forces
(4) Iraq constantly violates the CEASE FIRE AGREEMENT by shooting at UN surveillance aircraft and by trying to import by ship, military hardware such as medium-range missiles made in North Korea.
(5) UN invades Iraq after many warnings to STOP violating the CEASE FIRE AGREEMENT; the invasion was simply a resumption of the War that removed Iraq from Kuwait.