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.