War For Oil
The outbreak of modern wars are the work of many people, each with his/her own agenda.
So on one hand, trying to identify a single motivation for a war is a wasted effort, while on the other, naming a second motivation (or some actions not following from the first) is no negation of the first.
In Iraq: oil, strategic military position for further wars, popularity, a power demonstration, Israel's security and spreading phony democracy were all in the cards. In various people's minds. For example, as I argued, the two neocons Richard Perle (who co-authored Clean Break) and Paul Wolfowitz (the Combman nominated for President of the World Bank[*]) may had have rather different outcomes in mind (the former not minding a disintegration into fiefdoms).
Even on the issue of Iraqi oil, there were multiple motivations. Oil execs wanted to make money and their friends in government wanted campaign contributions (if the State spends more in the process is irrelevant - it's the taxpayers who lose not them), others wanted to bust OPEC, still others wanted to secure control of oil supplies ahead of Peak Oil.
As it now becomes clear, the above multiple motivations even led to conflicts. As a Greg Palast report for BBC revealed,
- the first secret plans (in 2001, before 9/11) aimed for indirect control after a coup (keeping oil state-owned and controlling it through the puppet government),
- pushed out by the neocon plan of selling off the oil business (to kill OPEC quotas with unlimited production), which is acknowledged by some as a big motivation for the Iraqi resistance,
- again stalled by oil industry people during the first months of the occupation, who also feared an outcome in which US companies are barred from privatisation and new Iraqi companies leave them out from trading, and didn't want to bust OPEC as high crude oil prices are good for their profits, too.
[*] I looked up vote shares in the IBRD and its Board Of Exececutive Directors (the latter votes on President) - USA 16.39%, Japan 7.86% and UK 4.30% are certainly on the Yes side (Jack Straw already gave his glowing recommendation), I guess Italy for the block it heads (3.50%) too, as well as, ridiculously, Kuwait for the Middle East block (2.91%), that's 34.96% so far. So some bribing & blackmailing is needed to get Wolfie in. (The Netherlands with its group is likely; if I add India, Russia, Saudi Arabia, and Switzerland with its group, it'd do it: 51.42%.)