Of course, we know that for most of history, this concept of "just war" was rarely observed. The capacity of human beings to think up new ways to kill one another proved inexhaustible, as did our capacity to exempt from mercy those who look different or pray to a different God. Wars between armies gave way to wars between nations – total wars in which the distinction between combatant and civilian became blurred. In the span of 30 years, such carnage would twice engulf this continent.

And while it's hard to conceive of a cause more just than the defeat of the Third Reich and the Axis powers, World War II was a conflict in which the total number of civilians who died exceeded the number of soldiers who perished. In the wake of such destruction, and with the advent of the nuclear age, it became clear to victor and vanquished alike that the world needed institutions to prevent another world war. And so, a quarter century after the United States Senate rejected the League of Nations – an idea for which Woodrow Wilson received this prize – America led the world in constructing an architecture to keep the peace: a Marshall Plan and a United Nations, mechanisms to govern the waging of war, treaties to protect human rights, prevent genocide, restrict the most dangerous weapons. In many ways, these efforts succeeded.

Yes, terrible wars have been fought, and atrocities committed. But there has been no Third World War. The Cold War ended with jubilant crowds dismantling a wall. Commerce has stitched much of the world together. Billions have been lifted from poverty. The ideals of liberty and self-determination, equality and the rule of law have haltingly advanced. We are the heirs of the fortitude and foresight of generations past, and it is a legacy for which my own country is rightfully proud. And yet, a decade into a new century, this old architecture is buckling under the weight of new threats.
The world may no longer shudder at the prospect of war between two nuclear superpowers, but proliferation may increase the risk of catastrophe. Terrorism has long been a tactic, but modern technology allows a few small men with outsized rage to murder innocents on a horrific scale. Moreover, wars between nations have increasingly given way to wars within nations. The resurgence of ethnic or sectarian conflicts; the growth of secessionist movements, insurgencies, and failed states – all these things have increasingly trapped civilians in unending chaos. In today's wars, many more civilians are killed than soldiers; the seeds of future conflict are sown, economies are wrecked, civil societies torn asunder, refugees amassed, children scarred. I do not bring with me today a definitive solution to the problems of war. What I do know is that meeting these challenges will require the same vision, hard work, and persistence of those men and women who acted so boldly decades ago. And it will require us to think in new ways about the notions of just war and the imperatives of a just peace. We must begin by acknowledging the hard truth: We will not eradicate violent conflict in our lifetimes.

There will be times when nations – acting individually or in concert – will find the use of force not only necessary but morally justified. I make this statement mindful of what Martin Luther King Jr. said in this same ceremony years ago: "Violence never brings permanent peace. It solves no social problem: it merely creates new and more complicated ones." As someone who stands here as a direct consequence of Dr. King's life work, I am living testimony to the moral force of non-violence. I know there's nothing weak – nothing passive – nothing naïve – in the creed and lives of Gandhi and King. But as a head of state sworn to protect and defend my nation, I cannot be guided by their examples alone. I face the world as it is, and cannot stand idle in the face of threats to the American people. For make no mistake: Evil does exist in the world. A non-violent movement could not have halted Hitler's armies. Negotiations cannot convince al Qaeda's leaders to lay down their arms. To say that force may sometimes be necessary is not a call to cynicism – it is a recognition of history; the imperfections of man and the limits of reason.

I raise this point, I begin with this point because in many countries there is a deep ambivalence about military action today, no matter what the cause. And at times, this is joined by a reflexive suspicion of America, the world's sole military superpower. But the world must remember that it was not simply international institutions – not just treaties and declarations – that brought stability to a post-World War II world. Whatever mistakes we have made, the plain fact is this: The United States of America has helped underwrite global security for more than six decades with the blood of our citizens and the strength of our arms. The service and sacrifice of our men and women in uniform has promoted peace and prosperity from Germany to Korea, and enabled democracy to take hold in places like the Balkans. We have borne this burden not because we seek to impose our will. We have done so out of enlightened self-interest – because we seek a better future for our children and grandchildren, and we believe that their lives will be better if others' children and grandchildren can live in freedom and prosperity. So yes, the instruments of war do have a role to play in preserving the peace.
And yet this truth must coexist with another – that no matter how justified, war promises human tragedy. The soldier's courage and sacrifice is full of glory, expressing devotion to country, to cause, to comrades in arms. But war itself is never glorious, and we must never trumpet it as such. So part of our challenge is reconciling these two seemingly inreconcilable truths – that war is sometimes necessary, and war at some level is an expression of human folly. Concretely, we must direct our effort to the task that President Kennedy called for long ago. "Let us focus," he said, "on a more practical, more attainable peace, based not on a sudden revolution in human nature but on a gradual evolution in human institutions." A gradual evolution of human institutions.
What might this evolution look like? What might these practical steps be? To begin with, I believe that all nations – strong and weak alike – must adhere to standards that govern the use of force. I – like any head of state – reserve the right to act unilaterally if necessary to defend my nation. Nevertheless, I am convinced that adhering to standards, international standards, strengthens those who do, and isolates and weakens those who don't.

The world rallied around America after the 9/11 attacks, and continues to support our efforts in Afghanistan, because of the horror of those senseless attacks and the recognized principle of self-defense. Likewise, the world recognized the need to confront Saddam Hussein when he invaded Kuwait – a consensus that sent a clear message to all about the cost of aggression. Furthermore, America – in fact, no nation – can insist that others follow the rules of the road if we refuse to follow them ourselves. For when we don't, our actions appear arbitrary and undercut the legitimacy of future interventions, no matter how justified. And this becomes particularly important when the purpose of military action extends beyond self-defense or the defense of one nation against an aggressor.

More and more, we all confront difficult questions about how to prevent the slaughter of civilians by their own government, or to stop a civil war whose violence and suffering can engulf an entire region. I believe that force can be justified on humanitarian grounds, as it was in the Balkans, or in other places that have been scarred by war. Inaction tears at our conscience and can lead to more costly intervention later. That's why all responsible nations must embrace the role that militaries with a clear mandate can play to keep the peace. America's commitment to global security will never waver. But in a world in which threats are more diffuse, and missions more complex, America cannot act alone. America alone cannot secure the peace. This is true in Afghanistan. This is true in failed states like Somalia, where terrorism and piracy is joined by famine and human suffering. And sadly, it will continue to be true in unstable regions for years to come. The leaders and soldiers of NATO countries, and other friends and allies, demonstrate this truth through the capacity and courage they've shown in Afghanistan.

But in many countries, there is a disconnect between the efforts of those who serve and the ambivalence of the broader public. I understand why war is not popular, but I also know this: The belief that peace is desirable is rarely enough to achieve it. Peace requires responsibility. Peace entails sacrifice. That's why NATO continues to be indispensable. That's why we must strengthen U.N. and regional peacekeeping, and not leave the task to a few countries. That's why we honor those who return home from peacekeeping and training abroad to Oslo and Rome; to Ottawa and Sydney; to Dhaka and Kigali – we honor them not as makers of war, but of wagers – but as wagers of peace. Let me make one final point about the use of force. Even as we make difficult decisions about going to war, we must also think clearly about how we fight it.

The Nobel Committee recognized this truth in awarding its first prize for peace to Henry Dunant – the founder of the Red Cross, and a driving force behind the Geneva Conventions. Where force is necessary, we have a moral and strategic interest in binding ourselves to certain rules of conduct. And even as we confront a vicious adversary that abides by no rules, I believe the United States of America must remain a standard bearer in the conduct of war. That is what makes us different from those whom we fight. That is a source of our strength. That is why I prohibited torture. That is why I ordered the prison at Guantanamo Bay closed. And that is why I have reaffirmed America's commitment to abide by the Geneva Conventions. We lose ourselves when we compromise the very ideals that we fight to defend. And we honor – we honor those ideals by upholding them not when it's easy, but when it is hard. I have spoken at some length to the question that must weigh on our minds and our hearts as we choose to wage war. But let me now turn to our effort to avoid such tragic choices, and speak of three ways that we can build a just and lasting peace.

First, in dealing with those nations that break rules and laws, I believe that we must develop alternatives to violence that are tough enough to actually change behavior – for if we want a lasting peace, then the words of the international community must mean something. Those regimes that break the rules must be held accountable. Sanctions must exact a real price. Intransigence must be met with increased pressure – and such pressure exists only when the world stands together as one. One urgent example is the effort to prevent the spread of nuclear weapons, and to seek a world without them. In the middle of the last century, nations agreed to be bound by a treaty whose bargain is clear: All will have access to peaceful nuclear power; those without nuclear weapons will forsake them; and those with nuclear weapons will work towards disarmament. I am committed to upholding this treaty.
It is a centerpiece of my foreign policy. And I'm working with President Medvedev to reduce America and Russia's nuclear stockpiles. But it is also incumbent upon all of us to insist that nations like Iran and North Korea do not game the system. Those who claim to respect international law cannot avert their eyes when those laws are flouted. Those who care for their own security cannot ignore the danger of an arms race in the Middle East or East Asia. Those who seek peace cannot stand idly by as nations arm themselves for nuclear war. The same principle applies to those who violate international laws by brutalizing their own people. When there is genocide in Darfur, systematic rape in Congo, repression in Burma – there must be consequences. Yes, there will be engagement; yes, there will be diplomacy – but there must be consequences when those things fail. And the closer we stand together, the less likely we will be faced with the choice between armed intervention and complicity in oppression. This brings me to a second point – the nature of the peace that we seek. For peace is not merely the absence of visible conflict. Only a just peace based on the inherent rights and dignity of every individual can truly be lasting. It was this insight that drove drafters of the Universal Declaration of Human Rights after the Second World War. In the wake of devastation, they recognized that if human rights are not protected, peace is a hollow promise.
And yet too often, these words are ignored. For some countries, the failure to uphold human rights is excused by the false suggestion that these are somehow Western principles, foreign to local cultures or stages of a nation's development. And within America, there has long been a tension between those who describe themselves as realists or idealists – a tension that suggests a stark choice between the narrow pursuit of interests or an endless campaign to impose our values around the world. I reject these choices. I believe that peace is unstable where citizens are denied the right to speak freely or worship as they please; choose their own leaders or assemble without fear. Pent-up grievances fester, and the suppression of tribal and religious identity can lead to violence. We also know that the opposite is true. Only when Europe became free did it finally find peace. America has never fought a war against a democracy, and our closest friends are governments that protect the rights of their citizens. No matter how callously defined, neither America's interests – nor the world's – are served by the denial of human aspirations. So even as we respect the unique culture and traditions of different countries, America will always be a voice for those aspirations that are universal. We will bear witness to the quiet dignity of reformers like Aung Sang Suu Kyi; to the bravery of Zimbabweans who cast their ballots in the face of beatings; to the hundreds of thousands who have marched silently through the streets of Iran. It is telling that the leaders of these governments fear the aspirations of their own people more than the power of any other nation. And it is the responsibility of all free people and free nations to make clear that these movements – these movements of hope and history – they have us on their side.