President Barack Obama issued a powerful defense of government on Monday, declaring that a decade of war was ending, the nation's economy was recovering and "America's possibilities are limitless" as he launched into a second term before a flag-waving crowd of hundreds of thousands.

Laying out an ambitious program for his coming four years, the president used his inaugural address to urge the country to join him in tackling a vast array of problems, from slowing climate change to honoring the dignity of men, women and children around the globe.

"My fellow Americans, we are made for this moment, and we will seize it, so long as we seize it together," Obama said. He also marked a new direction in foreign policy as the U.S. prepares to pull troops from Afghanistan, ending the country's longest war.

"We, the people, still believe that enduring security and lasting peace do not require perpetual war," the president said outside the Capitol, looking out across a huge crowd of people jammed should to shoulder on the National Mall below.

He challenged those who favor aggressive use of the powerful U.S. military to recall the policies of presidents past.

"We are also heirs to those who won the peace and not just the war, who turned sworn enemies into the surest of friends, and we must carry those lessons into this time as well," said Obama, who is under heavy pressure from the right-wing leadership of U.S. ally Israel and powerful voices in Congress to launch military strikes against Iran's nuclear program.

Obama said that the U.S. has a moral obligation to support democracy across the world. "We will support democracy from Asia to Africa; from the Americas to the Middle East, because our interests and our conscience compel us to act on behalf of those who long for freedom."

Obama's address touched on the broad gifts that bring the country together, and it pointed to the work ahead, "the realities of our time."

He said the country must make hard choices to reduce the massive deficit. "But we reject the belief that America must choose between caring for the generation that built this country and investing in the generation that will build its future," he said.

While he was officially sworn in Sunday, as required by law, the glitter of Inauguration Day - the parade down Pennsylvania Avenue toward the White House, the night of balls, the ceremonial beginning of a new four-year presidential term - still enlivened staid Washington. The celebration was pushed to Monday because January 20 fell on a Sunday this year. That placed the grand ceremony on the U.S. holiday marking the birthday of revered civil rights leader Martin Luther King.

Obama, the politician who rose improbably from a history as a community organizer in Chicago and a professor of constitutional law to the pinnacle of power, faces a nation riven by partisan disunity, a still-weak economy and an array of challenges abroad.

The president also faces a less charmed standing on the world stage, where expectations for him had been so high four years ago that he was given the Nobel Peace Prize just months into his presidency. "Only very rarely has a person to the same extent as Obama captured the world's attention and given its people hope for a better future," the Nobel announcement in 2009 read.

Monday's events had less of the effervescence of four years ago, when the 1.8 million people packed into central Washington knew they were witnessing history. Obama is now older, grayer and more entrenched in the politics he once tried rise above. Officials said crowds were about half what they were four years ago.

As he enters his second term, Americans increasingly see Obama as a strong leader, someone who stands up for his beliefs and is able to get things done, according to a survey by the Pew Research Center for the People & the Press. The survey shows him with a 52 percent job approval rating, among the highest rankings since early in his presidency. His personal favorability, 59 percent, has rebounded from a low of 50 percent in the 2012 campaign against Republican Mitt Romney.

When the partying is done on Monday, it's back to business for a president who is leading a nation that is, perhaps, as divided as at any time since the Civil War 150 years ago. That conflict put down a rebellion by southern states and ended slavery.

In light of the nation's troubled racial history, Obama's election to the White House in 2008 as the first black president was seen by many as a turning point. In his first inaugural address, Obama vowed to moderate the partisan anger engulfing the country, but the nation is only more divided four years on.

Obama guided the country through many crushing challenges after taking office in 2009: ending the Iraq war, putting the Afghan war on a course toward U.S.¬ withdrawal and saving the collapsing economy. He won approval for a sweeping health care overhaul.

Yet onerous problems remain, and his success in resolving them will define his place in history.