OSLO, Norway - President Barack Obama evoked the cause of a just war on Thursday, accepting his Nobel Peace Prize just nine days after sending 30,000 more U.S. troops to war in Afghanistan but promising to use the prestigious prize to "reach for the world that ought to be."

Protesters from the group The World Can't Wait demonstrate in New York against the awarding of the Nobel Peace prize to President Barack Obama. A humble Obama joined a list of revered Nobel peace laureates, but in a steely speech he warned he would not hesitate to wage war if it was "morally justified. "(AFP/Getty Images/Chris Hondros) Obama became the first sitting U.S. president in 90 years and the third ever to win the prize - some say prematurely. He and his wife, Michelle, whirled through a day filled with Nobel pomp and ceremony in this Nordic capital.

Obama delivered a Nobel acceptance speech that he saw as a treatise on war's use and prevention. He crafted much of the address himself and the scholarly remarks - at about 4,000 words - were nearly twice as long as his inaugural address.

"I face the world as it is," Obama said, refusing to renounce war for his nation or under his leadership, saying that he is obliged to protect and defend the United States.

"A nonviolent movement could not have halted Hitler's armies. Negotiations cannot convince al-Qaida's leaders to lay down their arms," Obama said. "To say that force is sometimes necessary is not a call to cynicism, it is a recognition of history."

The president laid out the circumstances where war is justified - in self-defence, to come to the aid of an invaded nation, or on humanitarian grounds, such as when civilians are slaughtered by their own government or a civil war threatens to engulf an entire region.

"The belief that peace is desirable is rarely enough to achieve it," he said.

He also spoke bluntly of the cost of war, saying of the Afghanistan buildup he just ordered that "some will kill, some will be killed."

"No matter how justified, war promises human tragedy," he said.

Obama also emphasized alternatives to violence, stressing the importance of both diplomatic efforts and tough sanctions to confront nations such as Iran or North Korea, which defy international demands to halt their nuclear programs, or those such as Sudan, Congo or Burma that brutalize their citizens.

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Text of Obama's Nobel Peace Prize acceptance speech

OSLO, Norway - The text of President Obama's Nobel Peace Prize acceptance speech, delivered Thursday in Oslo, Norway, as provided by the White House:

Your Majesties, Your Royal Highnesses, Distinguished Members of the Norwegian Nobel Committee, citizens of America, and citizens of the world:

I receive this honour with deep gratitude and great humility. It is an award that speaks to our highest aspirations - that for all the cruelty and hardship of our world, we are not mere prisoners of fate. Our actions matter, and can bend history in the direction of justice.

And yet I would be remiss if I did not acknowledge the considerable controversy that your generous decision has generated. In part, this is because I am at the beginning, and not the end, of my labours on the world stage. Compared to some of the giants of history who have received this prize - Schweitzer and King; Marshall and Mandela - my accomplishments are slight. And then there are the men and women around the world who have been jailed and beaten in the pursuit of justice; those who toil in humanitarian organizations to relieve suffering; the unrecognized millions whose quiet acts of courage and compassion inspire even the most hardened of cynics. I cannot argue with those who find these men and women - some known, some obscure to all but those they help - to be far more deserving of this honour than I.

But perhaps the most profound issue surrounding my receipt of this prize is the fact that I am the Commander-in-Chief of a nation in the midst of two wars. One of these wars is winding down. The other is a conflict that America did not seek; one in which we are joined by 43 other countries - including Norway - in an effort to defend ourselves and all nations from further attacks.

Still, we are at war, and I am responsible for the deployment of thousands of young Americans to battle in a distant land. Some will kill. Some will be killed. And so I come here with an acute sense of the cost of armed conflict - filled with difficult questions about the relationship between war and peace, and our effort to replace one with the other.

These questions are not new. War, in one form or another, appeared with the first man. At the dawn of history, its morality was not questioned; it was simply a fact, like drought or disease - the manner in which tribes and then civilizations sought power and settled their differences.

Over time, as codes of law sought to control violence within groups, so did philosophers, clerics and statesmen seek to regulate the destructive power of war. The concept of a "just war" emerged, suggesting that war is justified only when it meets certain preconditions: if it is waged as a last resort or in self-defence; if the forced used is proportional; and if, whenever possible, civilians are spared from violence.

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 is 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 and 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, 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.

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 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 and 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 that 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 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?s work, I am living testimony to the moral force of non-violence. I know there is nothing weak, nothing passive, nothing naive 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-Qaida?s leaders to lay down their arms. To say that force is sometimes 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 because in many countries there is a deep ambivalence about military action today, no matter the cause. At times, this is joined by a reflexive suspicion of America, the world?s sole military superpower.

Yet 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 other people's 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 and 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 irreconcilable truths - that war is sometimes necessary, and war is at some level an expression of human feelings. 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."

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 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-defence. 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 cannot insist that others follow the rules of the road if we refuse to follow them ourselves. For when we don?t, our action can appear arbitrary, and undercut the legitimacy of future intervention - no matter how justified.

This becomes particularly important when the purpose of military action extends beyond self-defence or the defence 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 is 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. 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 have 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 is why NATO continues to be indispensable. That is why we must strengthen UN and regional peacekeeping, and not leave the task to a few countries. That is why we honour those who return home from peacekeeping and training abroad to Oslo and Rome; to Ottawa and Sydney; to Dhaka and Kigali - we honour them not as makers of war, 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 that 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 honour those ideals by upholding them not just when it is easy, but when it is hard.

I have spoken to the questions that must weigh on our minds and our hearts as we choose to wage war. But let me turn now 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 change behaviour - 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 toward disarmament. I am committed to upholding this treaty. It is a centerpiece of my foreign policy. And I am 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 law by brutalizing their own people. When there is genocide in Darfur, systematic rape in Congo or repression in Burma - there must be consequences. 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 upon 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 all too often, these words are ignored. In some countries, the failure to uphold human rights is excused by the false suggestion that these are 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.

I reject this choice. 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 to these movements that hope and history are on their side.

Let me also say this: The promotion of human rights cannot be about exhortation alone. At times, it must be coupled with painstaking diplomacy. I know that engagement with repressive regimes lacks the satisfying purity of indignation. But I also know that sanctions without outreach - and condemnation without discussion - can carry forward a crippling status quo. No repressive regime can move down a new path unless it has the choice of an open door.

In light of the Cultural Revolution?s horrors, Nixon?s meeting with Mao appeared inexcusable - and yet it surely helped set China on a path where millions of its citizens have been lifted from poverty, and connected to open societies. Pope John Paul?s engagement with Poland created space not just for the Catholic Church, but for labour leaders like Lech Walesa. Ronald Reagan?s efforts on arms control and embrace of perestroika not only improved relations with the Soviet Union, but empowered dissidents throughout Eastern Europe. There is no simple formula here. But we must try as best we can to balance isolation and engagement, pressure and incentives, so that human rights and dignity are advanced over time.

Third, a just peace includes not only civil and political rights - it must encompass economic security and opportunity. For true peace is not just freedom from fear, but freedom from want.

It is undoubtedly true that development rarely takes root without security; it is also true that security does not exist where human beings do not have access to enough food, or clean water, or the medicine they need to survive. It does not exist where children cannot aspire to a decent education or a job that supports a family. The absence of hope can rot a society from within.

And that is why helping farmers feed their own people - or nations educate their children and care for the sick - is not mere charity. It is also why the world must come together to confront climate change. There is little scientific dispute that if we do nothing, we will face more drought, famine and mass displacement that will fuel more conflict for decades. For this reason, it is not merely scientists and activists who call for swift and forceful action - it is military leaders in my country and others who understand that our common security hangs in the balance.

Agreements among nations. Strong institutions. Support for human rights. Investments in development. All of these are vital ingredients in bringing about the evolution that President Kennedy spoke about. And yet, I do not believe that we will have the will, or the staying power, to complete this work without something more - and that is the continued expansion of our moral imagination, an insistence that there is something irreducible that we all share.

As the world grows smaller, you might think it would be easier for human beings to recognize how similar we are, to understand that we all basically want the same things, that we all hope for the chance to live out our lives with some measure of happiness and fulfilment for ourselves and our families.

And yet, given the dizzying pace of globalization, and the cultural levelling of modernity, it should come as no surprise that people fear the loss of what they cherish about their particular identities - their race, their tribe and, perhaps most powerfully, their religion. In some places, this fear has led to conflict. At times, it even feels like we are moving backwards. We see it in the Middle East, as the conflict between Arabs and Jews seems to harden. We see it in nations that are torn asunder by tribal lines.

Most dangerously, we see it in the way that religion is used to justify the murder of innocents by those who have distorted and defiled the great religion of Islam, and who attacked my country from Afghanistan. These extremists are not the first to kill in the name of God; the cruelties of the Crusades are amply recorded. But they remind us that no Holy War can ever be a just war. For if you truly believe that you are carrying out divine will, then there is no need for restraint - no need to spare the pregnant mother, or the medic, or even a person of one?s own faith. Such a warped view of religion is not just incompatible with the concept of peace, but the purpose of faith - for the one rule that lies at the heart of every major religion is that we do unto others as we would have them do unto us.

Adhering to this law of love has always been the core struggle of human nature. We are fallible. We make mistakes, and fall victim to the temptations of pride, and power, and sometimes evil. Even those of us with the best intentions will at times fail to right the wrongs before us.

But we do not have to think that human nature is perfect for us to still believe that the human condition can be perfected. We do not have to live in an idealized world to still reach for those ideals that will make it a better place. The non-violence practised by men like Gandhi and King may not have been practical or possible in every circumstance, but the love that they preached - their faith in human progress - must always be the North Star that guides us on our journey.

For if we lose that faith - if we dismiss it as silly or naive, if we divorce it from the decisions that we make on issues of war and peace - then we lose what is best about humanity. We lose our sense of possibility. We lose our moral compass.

Like generations have before us, we must reject that future. As Dr. King said at this occasion so many years ago: "I refuse to accept despair as the final response to the ambiguities of history. I refuse to accept the idea that the ‘isness' of man's present nature makes him morally incapable of reaching up for the eternal 'oughtness' that forever confronts him."

So let us reach for the world that ought to be - that spark of the divine that still stirs within each of our souls. Somewhere today, in the here and now, a soldier sees he?s outgunned but stands firm to keep the peace. Somewhere today, in this world, a young protester awaits the brutality of her government, but has the courage to march on. Somewhere today, a mother facing punishing poverty still takes the time to teach her child, who believes that a cruel world still has a place for his dreams.

Let us live by their example. We can acknowledge that oppression will always be with us, and still strive for justice. We can admit the intractability of deprivation, and still strive for dignity. We can understand that there will be war, and still strive for peace. We can do that - for that is the story of human progress; that is the hope of all the world; and at this moment of challenge, that must be our work here on Earth.