(Dec. 10) — President Barack Obama used his acceptance of the Nobel Peace Prize to make an unapologetic defense for the use of force, even unilateral force, to keep peace and defend his nation, but argued just as strongly that “no matter how justified, war promises human tragedy.”

Obama’s much-anticipated speech — or lecture, in the parlance of the Nobel Committee — was a bid to balance the nonviolent idealism of Mahatma Gandhi and Martin Luther King with his administration’s need to generate global support for the escalating conflict in Afghanistan. And the president acknowledged from the start that he stood before Norwegian royalty and the Nobel committee as the U.S. commander-in-chief who has just committed to sending an additional 30,000 troops there.

“We are at war, and I am responsible for the deployment of thousands of young Americans to battle in a distant land,” he said in his speech on Thursday. “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.”

Obama’s goals included reversing what he called a “reflexive suspicion of America” pervasive in the world, but he stressed that he would continue to make the defense of U.S. interests and security a priority.

“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,” Obama said. “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.”

His audience in Oslo, after welcoming the president with long applause, appeared stone-faced as he spoke and interrupted Obama’s speech just once to clap. The applause came near the end when he called on his listeners to “reach for the world that ought to be — that spark of the divine that still stirs within each of our souls.” But the president, who stuck to a multilateral tone through most of his address, received a lingering standing ovation as well.

Obama, who appeared to be tapped by the Nobel committee because for his reversal of many U.S. policies under President George W. Bush, also acknowledged “the considerable controversy that your generous decision has generated” in part “because I am at the beginning, and not the end, of my labors on the world stage.”

In awarding him the prize last October, the Norwegian Nobel Committee cited Obama’s “extraordinary efforts to strengthen international diplomacy and cooperation between peoples,” as well as his “vision of and work for a world without nuclear weapons.”>

Obama emphasized the importance of nuclear disarmament in his Oslo speech, and with it an undisguised plea for international support for the U.S. effort to make Iran forgo the potentially military side of its nuclear program.

“It is also incumbent upon all of us to insist that nations like Iran and North Korea do not game the system,” he said. “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.”

To that end, Obama contended that one key to building global peace is the development of “alternatives to violence that are tough enough to change behavior.”

For if we want a lasting peace, then the words of the international community must mean something,” he said. “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.”

In a tacit recognition that Bush administration policies had alienated many U.S. allies, Obama also declared that the U.S. must follow the same rules of war it demands from other nations, noting that he had ordered the closure of the prison at Guantanamo Bay and recommited to abiding by the Geneva Conventions.