Any use of massive violence such as that Washington is now threatening against Iraq is a terrible thing.
Everything we know about violence gives two clear lessons. First, the use of force always has unintended - often quite unpredictable - consequences. And second, war in the modern era always disproportionately harms civilians.
For these two reasons, there is a strong presumption in international law and international custom against any easy or voluntary recourse to war. War is still allowed in international law, yes - but only for self-defense, and only as a very last resort, after all avenues for peaceful resolution of differences have been exhausted.
Mr. President, you have no such justification for the war you now threaten against Iraq. There is still time to stand down the huge US expeditionary force and return to some version of the mix of containment and deterrence that has proved successful against Iraq until now - as it did against the much more threatening Soviet Union in an earlier era. Turn back from this war before its consequences come back to haunt you and the rest of the world.
Consequences that may be unpredictable? Ask Israeli Prime Minister Ariel Sharon what happened after he launched a massive assault against Lebanon in 1982. That campaign had two key similarities to the one you now threaten against Iraq. It was a war of "choice," not one imposed on Israel by other powers like some of its other wars. Secondly, Mr. Sharon's campaign aimed explicitly at bringing about "regime change" in Lebanon, as yours promises to do in Iraq.
At the military level, Sharon's warriors succeeded. Within two months, they controlled half of Lebanon including the capital Beirut. They forced Yasser Arafat's Palestinian guerrillas to leave the country, and "persuaded" Lebanon's parliament to vote in Israeli ally Bashir Gemayel as their new president.
Politically, however, Sharon's campaign did not go well. The continued presence of Israeli forces in the country catalyzed the birth of a new, much more militant Lebanese Muslim group called Hizbullah. Mr. Gemayel was assassinated.
Before 1982 ended, Israel was seeking to reduce its footprint in Lebanon. But it was unable to deal with the resistance that its presence provoked, and ended up staying in Lebanon an additional 18 years.
Israel (and Lebanon) bled profusely for all those years. (And the Palestinians? Their national movement simply changed its form. In 1987, it launched its first serious uprising - "intifada" - inside Gaza and the West Bank.)
No one in Israel today gives a favorable verdict to Sharon's 1982 campaign. One can only wonder how Americans 20 years from now will judge the results of a US war on Iraq.
Unintended outcomes? For this, look only at the American-led action in Kosovo in 1999. The purported reason for that war was to prevent Yugoslavia's Slobodan Milosevic from undertaking any further ethnic cleansing in Kosovo. But after the first American missiles landed in Belgrade, Mr. Milosevic only escalated his ethnic cleansing to unprecedented proportions, expelling 800,000 Kosovar civilians from their homes.
Now, Mr. President, you claim that one of your main aims is to prevent the further development of Saddam Hussein's weapons of mass destruction. But as Richard K. Betts argues in the current issue of Foreign Affairs, Mr. Hussein's reaction to a US strike against him may well be to use the very weapons from which you have sought to separate him. Indeed in Iraq, unlike in Kosovo, the nearly explicit aim of a US action is to force the opposing leader out of power completely. That well-known fact leaves Hussein with far less incentive for moderation than Milosevic had.
Shall we consider more unintended outcomes? How will it look in today's well-wired world if the US voluntarily launches a major war against Iraq for which there is no compelling Iraqi provocation and no formally expressed support from the UN?
In the National Security Strategy that the White House issued last September, you claimed that the US has a "right" of military preemption anywhere around the world. No other government anywhere supports that claim.
A unilateral attack on Iraq for which there is no completely evident justification and no UN mandate will be seen nearly everywhere as a policy simply of "might makes right." It is terrifying to think how other governments might follow that lead.
Meanwhile, what about North Korea? What about other urgent business overseas with Al Qaeda, with Afghanistan, with Palestinian-Israeli peacemaking? What about the domestic scene, with the gathering budget crises in the majority of our states? All those burning issues are now being brutally - and quite irresponsibly - shoved aside as the administration focuses its attention on Iraq. Where will all that lead?
Mr. President, there is still time to stop this war. True, the build-up toward it has already been very expensive. But you should not conclude that the fact of those already sunk costs locks you into a path of war against Iraq from which there is no escape. If you launch this war, then the cost - in dollars, in human suffering, and in unfolding strategic chaos around the Middle East and the world - will be unimaginably greater than anything you've spent to date.
Turn back. You have many friends in the US and around the world who will eagerly help you find a way to do so.
• Helena Cobban is the author of five books on international issues.