A DESPERATE Saddam Hussein firing poison gas missiles at Israel to shatter the fragile anti-Iraq alliance and Israel retaliating with nuclear weapons is one of the worrisome possibilities U.S. military planners have been discussing as President Bush nears his go or no-go decision on attacking Iraqi forces in Kuwait.

"Of course we've had to discuss that," said one Persian Gulf planner of the possibility that the crisis could result in the crossing of the 45-year-long firebreak between conventional and nuclear war. "That would be the worst possible outcome for everybody. That's why I think this whole thing is crazy."

This planner's view is shared by a number of silent but concerned military officers who fear desperate acts or accidental shootdowns will soon push events in the Persian Gulf out of anyone's control. But it does not appear to be the prevailing one. The Joint Chiefs of Staff have almost completed military preparations giving President Bush the option to order U.S. forces to attack Iraqi forces in Kuwait, including piling up supplies for 45 days of sustained combat.

It is an open secret that the war plan hammered out by the planners attached to the Joint Chiefs and the Central Command, which would run any Persian Gulf war, emphasizes bombing and fighting in the dark where U.S. night-vision capabilities give our forces a big edge over the Iraqis. Such operations are high risk as well as high-gain. U.S. desert warfare exercises at the National Training Center in California have shown with distressing regularity that our troops and their fanciest machines often get lost in the dark and stumble into the enemy's killing zone, something even more likely to happen in unfamiliar Kuwait where Iraqi artillery could inflict high casualties.

Before the confrontation reaches the point of no return, we owe it to the thousands of teenagers who are likely to die in a desert war to examine this worst case and to consider ways that armed conflict might be avoided without abandoning President Bush's primary objective of getting Iraqi forces out of Kuwait. The record shows the U.S. government and much of the press failed to conduct this kind of critical examination before we leaped into such destabilizing weapons as the MIRV multi-headed nuclear missile and into such military adventures as the Vietnam War. Former secretary of state Henry A. Kissinger, a goading force now for decisive action against Iraq, has said he wished he had thought through the long-range consequences of MIRV weapons before championing them. His stewardship of the Vietnam War, which included the invasion of Cambodia, further illustrated how wrong the smartest-sounding people can be about the long range consequences of U.S. military action. To understand what planners see when they look at what they call the "the worst-case scenario," assume Saddam concludes he is trapped and figures his only way out is to break up the uneasy alliance lined up against him, notably the United States, the Soviet Union, Saudi Arabia, Egypt, Syria and Iran. He decides to change the lineup from Iraq against the world to Arabs against Israel. He fires missiles into Israel knowing the Israelis will retaliate, triggering a Arab holy war against Israel and its sponsor, the United States. Such an outcome could keep the whole region in flames for years and demolish the bright hopes for the United States and Soviet Union to work together to keep order in the post-Cold War world.

How Israel would respond to a limited Iraqi attack is uncertain, like almost everything else in the Middle East. But what former secretary of state Dean Rusk told a small group of reporters two decades ago is instructive. He said he had warned an Israeli envoy against Israel's becoming the first country to use nuclear weapons in the Middle East. "We won't be the first," Rusk recalled the envoy replying, "but we won't be the second." Today's Israeli government is far more militant than the one Rusk cautioned in the 1960s and has a versatile nuclear arsenal at its disposal. Using nuclear missiles to level Saddam's chemical and nuclear facilities would be a tempting Israeli response. This would let the genie of tactical nuclear weapons out of the bottle at a time that a growing number of developing countries either have or are getting them, with India and Pakistan cases in point. Tactical nuclear war, with all its horror, would be legitimized.

Among the reasons some planners give for rejecting this worst-case scenario is that Saddam knows full well that Israel might retaliate with a nuclear strike he cannot match, thus deterring him from striking Israel with anything as provocative as poison-gas missiles. But the point is that nobody is sure what Saddam or Israel would do once the shooting started in the Persian Gulf nor how it would all end.

To keep the shooting from starting, what is wrong with updating what became known as the Aiken plan during the Vietnam War? Sen. George D. Aiken (R-Vt.) proposed that both sides declare victory and go home. The U.S. government, confident a little more blood and treasure would win the Vietnam War, laughed down the Aiken plan and ultimately lost the war after almost 58,000 American service people were killed. This time, before rejecting the Aiken plan as a joke, let us consider how it might work in the Persian Gulf. The United States and Iraq would agree to phased, mutual troop withdrawals from the inflammable region under United Nations supervision. U.N. designates, with the blessing of the deposed government of Kuwait, would select an area of Kuwait near the Iraqi border as a desert training base for peacekeeping forces. Or perhaps the United States alone could negotiate at least access to such a base and keep just enough forces there to serve as the plate-glass window that served us so well in Europe during the early days of NATO when Warsaw Pact forces looked far more threatening than Iraq's do today. Stepping over the border and breaking that window would risk war with the United States, not just Kuwait and/or Saudi Arabia. This would be a version of deterrence.

Kuwait in the past has refused to let the U.S. military use its territory, even at the time we were escorting Kuwaiti tankers through the Gulf. But the Iraqi invasion almost certainly has changed all that. The Central Command, which for want of a Persian Gulf base keeps its headquarters in Florida, will almost certainly be welcome in Kuwait if the traumatized emir gets back in power. One veteran combat leader of the 82nd Airborne Division, which is now in Saudi Arabia, said "a brigade on the ground would have been plenty" to deter Saddam from attacking Saudi Arabia. A similar force of about 3,000 troops in Kuwait backed up by air and naval power also would be a big enough plate-glass window to keep Saddam from going back into Kuwait, he reasoned.

Bush, if mutual withdrawals were negotiated and a peacekeeping force established, could claim he had achieved his objectives of forcing Iraq out of Kuwait, provided deterrence on the ground to further hostile acts and paved the way for the Kuwaiti people to re-establish their own government. He could also press for continuation of the embargo against Iraq in regard to items needed for its military machine, particularly chemical warfare, biological and nuclear arms. Satellite and other monitoring devices could keep constant track of Iraq's military forces and share the findings with neighboring Arab countries as well as Western allies.

And even if we did assassinate Saddam and bomb his military facilities, we might still not come out on top. The next Saddam could be worse. Bombed factories can be rebuilt, especially if the Soviets decide to help because the United States rejected its advice to negotiate a way out of the Persian Gulf crisis. A golden opportunity for U.S.-Soviet cooperation extending far beyond the little country of Kuwait would be lost.

For Saddam's part, he could tell his people he faced down the American devil in the Persian Gulf, won assurances from Soviet leader Mikhail Gorbachev that Palestinian grievances would be addressed under klieg lights in a Moscow conference and that he had taught oil-cheating Kuwait a lesson that would not be forgotten. If Saddam can fight Iran for eight years, go home with nothing gained and yet still declare victory, what would be so hard about his declaring victory after being in Kuwait for only three months? Who is left at home to challenge him?

As a former Marine commandant told me when President Reagan sent Marines into Lebanon, "I know how to get them in. What I don't know is how to get them out." Bush has gotten the Marines and thousands of other troops into the Persian Gulf. Now he has to find a way to get them out. Going to war before U.S. forces lose their enthusiasm and sandstorms get bad in December may look like the easiest way out. But the Vietnam experience suggests the longer way around may be the shortest way home.

George Wilson has covered military affairs for the Washington Post for two decades.