Was the war on Iraq an "aggressive war"? Oddly, it seems that there has been difficulty reaching consensus on the exact definition of that term, as shown by this article by one of the Nuremberg prosecutors.
Presumably a war would be "non-aggressive" if it were waged in response to the other country's attack on one's country (e.g., Pearl Harbor) or one's ally (e.g., Iraq's 1991 invasion of Kuwait). But Iraq did not attack the United States: as President Bush recently belatedly admitted, Iraq had nothing to do with the September 11, 2001 attacks against the United States. Iraq had seized Kuwait long before, but we successfully fought a war in 1991 to restore Kuwait's sovereignty, so that can hardly justify waging war against Iraq again in 2003.
What about weapons of mass destruction? Even assuming that the United States reasonably believed that Iraq had WMD's, that cannot suffice to make our war against Iraq "non-aggressive." Many countries, emphatically including the United States, have WMD's.
Perhaps our war against Iraq could properly be deemed non-aggressive if we reasonably believed that Iraq posed an imminent threat to us, for example if we had a strong basis for believing that it possessed large quantities of WMD's and intended to use them against us in the near future. (Ironically, conservatives are denying that the administration claimed that Iraq posed an imminent threat. Josh Marshall has a contest
to disprove that contention (scroll down to Oct. 30 2:18 p.m. entry). But if there was no imminent threat, that would only prove beyond a doubt that this was an aggressive war.)
But it appears that the administration's claims that Iraq had WMD's were massively over-hyped. Moreover, even if we had a basis for thinking that Iraq had some WMD's (this was commonly believed, even by opponents of the war), there was no apparent reason for thinking that Iraq had an imminent intent to use them against the United States. Our 1991 war against Iraq had surely engendered ill will by it against the United States, yet we had no evidence that Iraq had been involved in any actual or planned attacks in the intervening 12 years. Iraq's willingness to allow U.N. weapons inspectors in, and the fact that the inspectors found no WMD's, also strongly undercut any claim that our subsequent war against Iraq was non-aggressive.
The inescapable conclusion appears to be that our war against Iraq was an aggressive war that violated international law. Sadly, the United States has come a long way, in the wrong direction, since Supreme Court Justice Robert Jackson's August 12, 1945 statement that "our position is that no grievances or policies will justify resort to aggressive war. It is utterly renounced and condemned as an instrument of policy."