eurozone wars
From the Guardian

Almost 70% of the world's currency reserves - the money that nations use to finance international trade and protect themselves against financial speculators - takes the form of US dollars. The dollar is used for this purpose because it is relatively stable, it is produced by a nation with a major share of world trade, and certain commodities, in particular oil, are denominated in it, which means that dollars are required to buy them.

The US does very well from this arrangement. In order to earn dollars, other nations must provide goods and services to the US. When commodities are valued in dollars, the US needs do no more than print pieces of green paper to obtain them: it acquires them, in effect, for free. Once earned, other nations' dollar reserves must be invested back into the American economy. This inflow of money helps the US to finance its massive deficit.

The only serious threat to the dollar's international dominance at the moment is the euro. Next year, when the European Union acquires 10 new members, its gross domestic product will be roughly the same as that of the US, and its population 60% bigger. If the euro is adopted by all the members of the union, which suffers from none of the major underlying crises afflicting the US economy, it will begin to look like a more stable and more attractive investment than the dollar. Only one further development would then be required to unseat the dollar as the pre-eminent global currency: nations would need to start trading oil in euros.

I think there are problems with the eurozone explanation of the war, although I do not put it past the economic folly of the war party to invade Iraq for this reason. It should be remembered that the British empire was once known as the sterling area and that for some time after 1945 a series of British governments fought desperately (if unsuccessfully) to maintain the pound sterling as a global currency. That effort failed because the British economy was not strong enough to maintain itsindependence of the US dollar.

And that's the final imperial folly. The first province of the American imperium is not Iraq, but the United States.