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. (Applause.) 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.