In strikingly tough-minded language, President Barack Obama accepted the Nobel Peace Prize in Oslo on Thursday, mixing a call for peace and idealism with a stark reminder that he commands the U.S. military and that war is sometimes necessary.

Obama, who just last week requested 30,000 more troops be sent to Afghanistan, may have disconcerted his Norwegian hosts with statements such as, “the instruments of war do have a role to play in preserving the peace.— The president was interrupted by applause only twice.

Obama acknowledged the controversy that has attended his selection for the prize, saying that his “accomplishments are slim— compared to others have received the prize. He asserted that there are those alive today who are more deserving of it then him. “In part, this is because I am at the beginning, and not the end, of my labors on the world stage,— he said.

Obama termed his success “as a direct consequence— of Dr. Martin Luther King Jr., praising the example set by King and Mahatma Gandhi of nonviolence. But then he turned to a kind of cold realism about war that he has rarely displayed before.

“As a head of state sworn to protect and defend my nation, I cannot be guided by their examples alone,— Obama said of Gandhi and King. “I face the world as it is, and cannot stand idle in the face of threats to the American people,— he continued. “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.—

But in a clear effort to set himself apart from his predecessor, former President George W. Bush, Obama emphasized that the practice of war must hold to certain ideals and standards. He said countries must seek to work together to oppose evil and aggression instead of acting unilaterally.

“I believe that the United States of America must remain a standard bearer in the conduct of war,— Obama said. “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 Guántanamo Bay closed. And that is why I have reaffirmed America’s commitment to abide by the Geneva Conventions.—

Obama said countries must negotiate with others whose behavior they wish to change, but he argued that when diplomacy doesn’t work sanctions must be applied rigorously.

“Yes there will be engagement, yes there will be diplomacy, but there must be consequence when those things fail,— he said.

But he also asserted that countries can still have a sense of idealism about a peaceful future. “We do not have to think that human nature is perfect for us to still believe that the human condition can be perfected,— he said. “We do not have to live in an idealized world to still reach for those ideals that will make it a better place.—

The president was interrupted for only the second time by applause with a call to “reach for the world that ought to be that spark of the divine that still stirs within each of our souls.—

But he then reminded his audience that the striving for peace coexists with the need for war.

“Clear eyed, we can understand that there will be war, and still strive for peace,— he said.