Odd Andersen, Associated Press
President Barack Obama receives his Nobel Peace Prize medal and diploma Thursday from Nobel committee chairman Thorbjorn Jagland.

WASHINGTON — By using his Nobel Peace Prize acceptance speech Thursday to justify expanding the U.S.-led war in Afghanistan, President Barack Obama won over some Republican critics at home, even as he preached messages of multilateralism, diplomacy and civil disobedience that resonate in anti-war circles around the world.

In a 36-minute speech in Oslo, Obama defended last week's announcement that he'll send 30,000 to 35,000 more troops to Afghanistan. He discouraged other nations' "reflexive suspicion of America," recalling how Europe survived thanks to U.S. intervention in World War II. He spoke of "just war."

The president even invoked one of the favorite qualifiers of his predecessor, George W. Bush, whose legacy he campaigned against last year. Obama said, "Evil does exist in the world."

While accepting an international honor that in the short term also has been somewhat of a political albatross, Obama sought to convey sufficient humility. He acknowledged "the considerable controversy" over receiving the peace prize after less than a year on the job.

Given the stature of some past winners and the ordeals faced by humanitarian leaders who have never won, the president said, "I cannot argue with those who find these men and women, some known, some obscure to all but those they help, to be far more deserving of this honor than I."

Obama called on other nations to step up their commitments to U.N. peacekeeping efforts, nuclear disarmament and imposing serious sanctions on regimes that pose a threat to world stability.

"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 seek peace cannot stand idly by as nations arm themselves for nuclear war."

In Norway, some protesters implored the president to go earn his prize, while back in the U.S., civil libertarians said that Obama still hadn't matched his campaign rhetoric on human rights or moved away sufficiently from Bush-era policies on issues such as state secrets.

However, Newt Gingrich, the Republican former speaker of the House of Representatives and an ever-possible presidential candidate, said on WNYC radio that Obama's speech was "actually very good."

Gingrich said "having a liberal president who goes to Oslo on behalf of a peace prize and reminds the committee that they would not be free, they wouldn't be able to have a peace prize, without having force. ... I thought, in some ways, it's a very historic speech."

House Minority Leader John Boehner, R-Ohio, offered similar praise through his spokeswoman Antonia Ferrier: "As President (Ronald) Reagan said, Republicans believe in peace through strength, and we were pleased that today President Obama addressed and defended our mission in Afghanistan, where success is the only option."

Scholars were intrigued by the duality of Obama's speech and his underlying thinking.

"Evil in the world? 'Just war'? What was hovering over this speech was 'W,' " said Aaron David Miller, of the Woodrow Wilson International Center for Scholars in Washington, using a nickname for Bush.

"It's an exquisite-but-must-be-painful irony for him to accept. He couldn't come to Oslo and give any other speech than the one he gave."

One explanation, Miller said, was political expediency: "You stand up to the Euros and tree-huggers, you co-opt the Republicans, and you set to rest the notion of the Kumbaya, tree-hugger president, to remain politically relevant.

"The second explanation, which is equally intriguing, would be that the reason he gave this speech is that, as a consequence of the legacy he bequeathed, George W. Bush has created parameters within which future presidents are going to have to operate."

Georgetown University historian Michael Kazin called the speech "classic Obama ... both a classic statement of liberalism in foreign policy but, like Obama, pragmatic in trying to face hard choices. He's acknowledging he's not a peacemaker, that that's not his primary job description."

Kazin said Obama's anti-war rhetoric shouldn't be dismissed, however. The president spoke of belief in a "North Star" of faith in human progress, and the power of the nonviolent messages of Martin Luther King Jr. and Mohandas Gandhi. "War itself is never glorious," Obama said, and on its own can't bring peace.

Republicans "like him saying America is a moral force in the world and has to fight wars to press its moral claim," Kazin said. "But if you read his speech more closely, he's clearly, I think, talking about injustice in the world and not just injustice by people who don't like the United States. Some people on the right believe their own rhetoric too much, that he's somehow un-American. That's never been true."

The president said in Oslo, "We must try as best we can to balance isolation and engagement, pressure and incentives, so that human rights and dignity are advanced over time."

Kazin and Miller said that wasn't specific enough to serve as an "Obama Doctrine."

Still tied to Iraq, mired in Afghanistan and Pakistan, chasing al-Qaida and unable to shake Iran and North Korea or to get Israel and the Palestinians to deal, the president also said, "I face the world as it is, and cannot stand idle in the face of threats to the American people.

"A nonviolent movement could not have halted Hitler's armies. Negotiations cannot convince al-Qaida'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."