After all, the general consensus among commentators was that Mr. Obama had won the prize because he represented such a change from his predecessor, George W. Bush, whose rhetoric and foreign policy were anathema to most Europeans.
And yet while Mr. Obama offered a nuanced speech laying out what some have already started to call an Obama Doctrine, he also made an unmistakable argument for the legitimacy of war – sometimes using the sort of phrases that called to mind the very words of the man he replaced.
"Evil does exist in the world," Mr. Obama said as part of a long argument in favor of the concept of a "just war."
That line brought to mind Mr. Bush's repeated invocation of evil – including his argument in the wake of the Sept. 11 attacks that "our responsibility to history is already clear: to answer these attacks and rid the world of evil."
President Obama said there are times when "the use of force [is] not only necessary but morally justified"; he argued that he "cannot stand idle in the face of threats to the American people."
Cue Mr. Bush on the USS Abraham Lincoln, May 2003: "Any outlaw regime that has ties to terrorist groups or seeks to possess weapons of mass destruction is a grave danger to the civilized world and will be confronted."
Mr. Obama also made the case for American exceptionalism, an attitude associated more with his predecessor.
America, he said, "has helped underwrite global security for more than six decades with the blood of our citizens and the strength of our arms."
"We have borne this burden not because we seek to impose our will," said Mr. Obama. "We have done so out of enlightened self-interest -- because we seek a better future for our children and grandchildren, and we believe that their lives will be better if others' children and grandchildren can live in freedom and prosperity."
To be sure, the speech also included the sort of nuance that we've come to expect from Mr. Obama: He called himself a "living testimony to the moral force of non-violence" and said war is "never glorious" and "at some level is an expression of human folly."
He said he was seeking "alternatives to violence that are tough enough to actually change behavior." He spoke of the "spark of the divine that still stirs within each of our souls."
"He is a subtle guy," New York Times columnist Tom Friedman said after the speech. "It wasn't George W. Bush, you know, 'we're out there promoting freedom in every corner of the world, this is where we are.'"
Yet while the message may not have exactly mirrored the arguments of Mr. Bush, the takeaway, in the end, was not much different: The world is a messed-up place, and America is justified and right in confronting that reality even if that means using military force.
In no uncertain terms, he said that attitude is wrong.
"A non-violent movement could not have halted Hitler's armies," said Mr. Obama. "Negotiations cannot convince al Qaeda's leaders to lay down their arms. To say that force may sometimes be necessary is not a call to cynicism -- it is a recognition of history; the imperfections of man and the limits of reason."
It is no surprise that the president came to Oslo to make the case for war: It would have been impossible to ignore the fact that one week ago he made the decision to send 30,000 more troops into Afghanistan, an eight-year-old conflict that critics say has no clear end in sight. But one can safely assume that the members of the Peace Prize Committee did not honor Mr. Obama in an effort to give him a platform to lay out his justification for American intervention abroad.
Yes, this was in part a speech about human rights, about the perils of religious extremism, about preventing the spread on nuclear weapons, and about – in the clearest repudiation of Mr. Obama's processor – the importance of abiding by the Geneva Conventions and not torturing ones enemies. It was, in those portions, the speech the committee might have expected.
But it was also a speech in defense of war – and an argument that America alone should not shoulder the burden for waging it.
"I understand why war is not popular, but I also know this: The belief that peace is desirable is rarely enough to achieve it," he said. "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."
He added: "America alone cannot secure the peace."
The address may have come with the subtlety and nuance that Mr. Bush too-often lacked, and it may have taken a long view in a way that Mr. Bush often failed to do.
But at its heart was a message upon which Mr. Bush and Mr. Obama, for all their perceived differences, seem to wholeheartedly agree.
More on Obama's Nobel Prize:
Obama Offers Treatise on War and Peace
Obama: U.S. Standard Bearer for Peace
Washington Unplugged: Obama In Oslo: War For Peace
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?