To add to what friedo said, WWII was a prolonged affair lasting for several years that involved driving occupying forces out of several nations. Weapons stockpiles were quickly exhausted, and keeping up with the huge new demand created more jobs. There were more jobs than there were people to fill them.
Not only was WWII prolonged, but two-high technology adversaries were involved. Huge sums were spent on research to turn novelties like radar, rockets, jet aircraft, computers, and nuclear fission into useable tools. Once refined, factories were built to produce them in quantity. After the war the factories kept going not only by returning to domestic production, but also by developing civilian adaptations such as microwave ovens, space probes, commercial jet aircraft, and nuclear power plants.
There was also rationing of almost everything in WWII. While everyone was working in defense plants, there were few consumer products being produced that they could buy. Even shoelaces were hard to find. When the war was over everyone had saved up plenty of money for the new domestic products that factories started turning out, so there was no post-war economic slump.
Then there came the cold war, where many of our allies had suddenly turned to enemies. Spending stayed high for for decades, funding both defense and prestiege, such as the “space race.”
Iraq is a situation that could be resolved with one bullet.
So I look for a short war where the overall effect on the economy will be temporary and not terribly dramatic. It will cause various markets to fluctuate that might not have otherwise seen much effect. At the end I think it will average out and the economy will be better, but only a little.
At the end, the question is “what happens to investor confidence?” Ultimately the market is driven by how good investors feel about things in general. If the feeling is that September 11 is pretty much over and it’s time to get back to business, I think we’ll see a steady increase lasting for several years.