What we have left behind are the certitudes and simplifications of the past -- and that's not necessarily a bad thing. During the cold war, policymakers could justify every act with one word: containment. We got the big things right -- containment was the right policy and it succeeded and we won the cold war and we are all far, far better for it. But even the best policy can become the worst straitjacket if it is pursued too rigidly and reflexively -- as we saw in Vietnam.

Now, we have the opportunity to think anew about the best ways to promote America's interests and ideals. Our tools of first resort remain diplomacy and the power of our example. But sometimes, we have to rely on the example of our power. We face no more important questions than when and how to use it. From our experience in countering traditional aggression -- as in the Persian Gulf -- and contending with more novel crises -- as in Haiti and Bosnia -- there are some principles on the use of force that I would like to discuss with you.

First, let me cite one underlying and enduring principle: We will always be ready to use force to defend our national interests. Until human nature changes, power and force will remain at the heart of international relations.

This begs the question of just what those interests are that we will defend. I would cite seven circumstances, which, taken in some combination or even alone, may call for the use of force or our military forces:

1. To defend against direct attacks on the United States, its citizens, and its allies; 2. To counter aggression; 3. To defend our key economic interests, which is where most Americans see their most immediate stake in our international engagement; 4. To preserve, promote and defend democracy, which enhances our security and the spread of our values; 5. To prevent the spread of weapons of mass destruction, terrorism, international crime and drug trafficking; 6. To maintain our reliability, because when our partnerships are strong and confidence in our leadership is high, it is easier to get others to work with us, and to share the burdens of leadership. 7. And for humanitarian purposes, to combat famines, natural disasters and gross abuses of human rights with, occasionally, our military forces.

Not one of these interests by itself -- with the obvious exception of an attack on our nation, people and allies -- should automatically lead to the use of force. But the greater the number and the weight of the interests in play, the greater the likelihood that we will use force -- once all peaceful means have been tried and failed and once we have measured a mission's benefits against its costs, in both human and financial terms.

In Haiti, when we saw democracy stolen from its people, a reign of brutality take hold in our hemisphere, a flood of refugees to our shores, international agreements consistently violated and efforts to resolve the impasse through negotiations and sanctions fail, the case for intervention was compelling. In Bosnia, the worst atrocities in Europe since World War II -- a dangerous fire at the very heart of the continent -- our commitments to our NATO allies and a peace agreement the parties were calling on us to secure required us to act, and the President decided to do so.

But more than the "when" of using force, Haiti, Bosnia and some other recent interventions highlight principles that get at a harder question, perhaps, and that is the "how" we should use force.

First, threatening to use force can achieve the same results as actually using it -- but only if you're prepared to carry through on that threat. The best-trained, best-equipped and best-prepared fighting force in the world has a unique ability to concentrate the minds of our adversaries without firing a shot. In Haiti, when the military regime learned that the 82nd Airborne literally was on the way, those leaders got out of the way. In the Persian Gulf, as soon as President Clinton moved American forces into the region, Iraq moved its troops away from Kuwait. And by backing diplomacy with the presence of U.S. military forces to deter attack on the South, we convinced North Korea to freeze its dangerous nuclear weapons program.

A second principle is that the selective but substantial use of force is sometimes more appropriate than its massive use -- provided that the force is adequate to the task, and then some. President Clinton refused to engage our troops in a ground war in Bosnia because he knew that no outside power could force peace on the parties. To do so would have risked a Vietnam-like quagmire. But this summer, the combination of NATO's heavy and continuous air strikes, Bosnian and Croat gains on the ground, and our determined diplomacy convinced the Bosnian Serbs to stop making war and start making peace. Now, our troops are in Bosnia not to fight a war through a massive intervention, but to secure a peace they produced through the deliberate, calibrated use of force.

A final principle is this: Before we send our troops into a foreign country, we should know how and when we're going to get them out. Sounds simple, even obvious. But it is not an uncontroversial point. But carefully defined exit strategies for foreign interventions have not been a hallmark of our foreign policy in recent decades. Now they are -- and that makes sense for America, for America's military and for the people we're trying to help.

I don't want to be doctrinaire in asserting an exit strategy doctrine. When it comes to deterring external aggression -- as in the Persian Gulf or the Korean Peninsula -- or fighting wars in defense of our most vital security interests, a more open-ended commitment is necessary. But increasingly, our interests require that our military keep peace in the wake of internal conflicts. For these operations to succeed, tightly tailored military missions and sharp withdrawal deadlines must be the norm.

The logic is this: The first step is to give our Armed Forces a clear mission with achievable military -- I repeat, military -- goals, as President Clinton did in both Haiti and Bosnia. In Haiti, we asked our Armed Forces to return the elected government to power and restore a secure climate so that civilians could train a police force, hold elections and begin reconciliation. In Bosnia, our soldiers are overseeing the implementation of the military side of the Dayton accords -- separating the armies, maintaining the cease-fire, securing transferred territory -- while civilian authorities help the Bosnian people rebuild their lives and their land. In both places, our troops are highly trained and heavily armed, with very clear rules of engagement. And the Executive Branch and Congress are united in their commitment to our military's goals and success, as they were in Operation Desert Storm.

Contrast these operations with Vietnam, Lebanon and Somalia. There, clear and achievable missions for our military were not defined. In Vietnam, our society blamed our soldiers for a defeat that was not theirs. Because we neglected to ask the right questions and establish clear military goals from the start, our fighting men and women paid a terrible price, both in Vietnam and on their return home. We must never put them in that position again. Never. It just mustn't happen. The next step, then having defined clear military missions, is to set deadlines for withdrawal based on the accomplishment of those missions. In Haiti, our military leaders informed the President that our troops could complete their military tasks in about a year and a half and in Bosnia in about one year -- and they will.

Here's why setting deadlines is so important:

Neither we nor the international community has either the responsibility or the means to do whatever it takes for as long as it takes to rebuild nations. There are many reasons for this.

First, providing a security blanket for an indefinite period without making clear it's on loan -- and not for keeps -- only gives those we are trying to help the comfort to believe that they can evade their own responsibilities for the future of their own societies. It creates unreasonable expectations that the hard work will be done for them not by them.

Second, assuming too much responsibility for a nation's future tends to undercut the very government you are trying to help. In Vietnam, the more we assumed responsibility for a weak Saigon administration, the more dependent it became -- and the more open to charges it was a puppet regime beholden to foreigners. Unless you make clear that your mission is limited in scope and duration, you risk de-legitimating a government in the eyes of its own people and you will lose a conflict that is, at its heart, political, and not military.

Third, overstaying one's welcome ultimately breeds resentment of our presence and provides an easy target for blame when things go wrong. And believe me, that target will be us.

By carefully defining the mission and clearly setting a deadline, we serve notice that our only goal is to give governments and people the breathing room they must have to tackle their own problems. This "tough love" policy may sound harsh to some. It may strike others as a gamble. But consider the alternative: self-defeating efforts to take on responsibilities that are not ours -- to create unsustainable dependencies instead of giving nations a chance to act independently. It is a dangerous hubris to believe we can build other nations. But where our own interests are engaged, we can help nations build themselves -- and give them time to make a start at it.

I believe we can see the benefits of our exit strategy doctrine in Haiti and Bosnia.

Given the chance, the Haitian people quickly focused on the ballot, not the bullet; on trade, not terror; on hope, not despair. In just a year and a half, with our civilian help, they have completed presidential, parliamentary and local government elections; trained a police force, that is as yet imperfect, but showing great progress. They have dramatically, despite problems, improved the human rights situation and begun to reverse the economic decline of the coup years. Haiti remains the poorest nation in the Americas. There is no guarantee democracy will take hold or the economy will prosper. But its people now have a real chance to build a better future for themselves and their children -- and for the U.S. forces who have acted in Haiti with such strength and with such skill are leaving when we promised they would, we can say "mission accomplished."

The same logic applies in Bosnia and the same opportunity lies before the people of Bosnia. Its people understand they have a window of opportunity that our military opened and will hold open for the remainder of this year to decide their future in peace: to freely choose their own leaders in elections later this summer; to begin to rebuild their roads and schools, their factories and their hospitals; to reunite children with their parents and families with their homes. At the end of this year, when our troops leave, we can reasonably hope that the people of Bosnia will have developed a greater stake in peace than war -- that peace will have taken on a life and logic of its own. That is all that can be asked of us.

But let me make one point absolutely clear -- the breathing room our military is providing in Haiti and Bosnia must be filled with the oxygen of economic reconstruction assistance. What we call civilian implementation is the vital and necessary companion to any peacekeeping operation. Our allies agree. That's why they are providing about 80 percent of the civilian assistance for Haiti and for Bosnia. The sooner people in conflicted countries recover the blessings of a normal life, the surer the chances our troops will leave behind them a legacy of peace and hope as they are doing in Haiti.