In his lecture today in Oslo accepting the Nobel Peace Prize, the president sought to address the incongruity of an American Commander-in-Chief, at war in two countries, receiving such an honor.
It brought to mind Edwin Starr's 1970 hit song which repeatedly asked and answered the musical question: "War. What is it good for? Absolutely nothing!"
To the contrary, Mr. Obama argued forcefully that war is often inevitable and the only path to peace.
"I understand why war is not popular," said Mr. Obama, "but I also know this: The belief that peace is desirable is rarely enough to achieve it."
In a 35-minute speech at the end of a grand ceremony in which he was presented with the Nobel Peace Prize medal and diploma, Mr. Obama said the world must acknowledge "the hard truth" that violent conflict will not be eradicated in our lifetimes. But that, he added, is not necessarily a bad thing.
"There will be times when nations -- acting individually or in concert -- will find the use of force not only necessary but morally justified," he said.
Mr. Obama countered pacifist views in many countries, which to him, amount to "a deep ambivalence about military action today, no matter what the cause."
He said it's a position that might be understandable and acceptable for private citizens, but not for him as chief of state of the world's sole superpower.
"War is sometimes necessary," he asserted. But in the same sentence, he also said "war at some level is an expression of human folly."
He spoke at length about the concept of "a just war." As an example, he cited World War II, saying "it's hard to conceive of a cause more just than the defeat of the Third Reich and the Axis powers."
"There will be times," he said, "when nations -- acting individually or in concert -- will find the use of force not only necessary but morally justified." He said force can be justified on humanitarian grounds – as it was in the Balkans and elsewhere.
He acknowledged that his heroes, and previous Peace Prize winners, Dr. Martin Luther King, Jr. and Mohandas Gandhi, spent their lifetimes making the case for the moral force of non violence.
"But as a head of state sworn to protect and defend my nation, I cannot be guided by their examples alone," said Mr. Obama. "I face the world as it is and cannot stand idle in the face of threats to the American people."
At the same time, he vowed adherence to society's rules of war: the Geneva Conventions.
"All nations – strong and weak alike – must adhere to standards that govern the use of force," he said, adding that "no nation can insist that others follow the rules of the road if we refused to follow them ourselves."
Though he chooses not to speak of the war on terrorism, Mr. Obama saved his strongest condemnations for the warfare waged by Islamic extremists.
"Religion is used to justify the murder of innocents by those who have distorted and defiled the great religion of Islam – and attacked my country from Afghanistan," he said.
Speaking nine days after announcing his intention to send another 30,000 American troops to fight in Afghanistan, Mr. Obama was clearly referring to al-Qaeda and the Taliban when he said "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 the Red Cross worker, or even a person of one's own faith," he said.
He spoke of "a warped view of religion" incompatible with the concept of peace and the very purpose of faith.
Its practitioners are the enemy against which Mr. Obama, now armed with the moral authority of a Nobel Peace Prize, is arraying upwards of a 100,000 troops to defeat in Afghanistan.
More on Obama's Nobel Prize:
Obama: U.S. Standard Bearer for Peace
Obama Offers Treatise on War and Peace
Obama Channels George W. Bush
Photos: Obama in Norway
Full Text of Obama's Remarks
Video: Obama's Nobel Prize Speech (excerpts)
Analysis: Can Obama Deliver on Nobel Peace Prize Goals?
Who Should Get Obama's Nobel Prize Cash?