Washington ? The best-equipped military force in world history should quickly and decisively defeat a war-ravaged, poverty-stricken country on the other side of the world. This statement could have been at least as true about Vietnam in 1964 as it is about Iraq today. And while Iraq is nothing like Vietnam, they share two things in common: first, once war starts, things may turn out far differently than planned. Second, it is therefore worthwhile to think hard about the unplanned possibilities before we rush into war.

The first unplanned possibility is that a war against Iraq substantially increases the already high levels of hostility directed against the United States — while being liked in this world may not be everything, being too unpopular comes with some real price tags.

For example, Kentucky Fried Chicken franchises are doing badly in Pakistan these days. Two of them were ransacked by mobs after the U.S. attack against Afghanistan last year. The problem of U.S. chicken snack sales in South Asia may not be of much concern, but if an attack on Iraq causes the United States to be seen as a brutal aggressor throughout the developing world — a possibility suggested by recent polls — U.S. businesses might have genuine cause for concern. Retail establishments from McDonald’s to Wal-Mart could see sales and opportunities for global expansion severely curtailed.

Nor are retail companies the only ones affected. Boeing may face a new obstacle — adverse public opinion in various countries — in its worldwide competition with Airbus. Microsoft might see more countries and companies opting for open source software. And the music and movies produced by Disney and AOL-Time Warner may spread more freely via the Internet and bootlegs than through authorized sales and distribution that fetch royalties.

Moreover, it will not just be the negative impact on U.S. companies abroad that severely affects our economy, particularly if the war takes a bad turn.

One widely discussed scenario suggests that a large part of Mideast oil could be removed from world markets for a significant period if Saddam Hussein sabotages his own oil fields before being removed from power. Or, regionally, an Iraqi attack or domestic insurrection in Saudi Arabia or other gulf states could cut production, again sending oil prices skyrocketing and virtually guaranteeing a second recessionary dip.

As severe as the economic impact might be on the United States, the effects are likely to be even worse in developing countries. They would get hit by the higher oil prices and would also see a sharp decline in their exports, most of which go to the wealthier nations.

At the same time, developing countries would see a sharp rise in local interest rates, as money flees to safe havens in Europe and the United States. This could derail heavily indebted economies such as Brazil and Uruguay — and in fact could sentence every country in South America to another “lost decade” after 20 years of stagnating living standards.

But the worst scenario and possibility is an upturn in terrorism. The Sept. 11 attack has already cost us tens of billions of dollars in new spending on anti-terrorism measures and activities and prompted the creation of a new Cabinet position and government department. But our fear of terrorism and concerns about security could become far higher. At present, the threat of terrorism in the United States is nowhere near as great as in Israel.

If our fears lead us to adopt Israeli type precautions, the costs would be enormous. For example, the cost of stationing an armed guard at the entrance of every retail outlet in the country — a standard practice in Israel — would be more than $100 billion a year. The full cost of countering a vastly expanded terrorist threat would be staggering, leading to years of economic stagnation and rising unemployment — in addition to psychological impact nationally from lost lives and rising fear.

This is all speculation. Possibly, an attack on Iraq will go like clockwork — meeting little resistance and arousing little concern from people elsewhere in the region or the world. But we should at least consider the equally likely prospects that things will not turn out that way. What is certain is that the decision-makers in Washington will not be the ones who pay the price if they turn out to be wrong.