Barack Hussein Obama II, born August 4, 1961, is the 44th and current President of the United States, and the first black US president. He defeated Republican rival John McCain in the general election of 2008, and was inaugurated as president on January 20, 2009. Obama was named the 2009 Nobel Peace Prize laureate in October 2009. He was re-elected president in November 2012, defeating Republican nominee Mitt Romney.
Barack Obama pledges support for the working and middle class in America
Just as Theodore Roosevelt saw himself as a protector of the poor a century ago, Barack Obama promises help early in a new century
There's no doubt any more where President Barack Obama wants America, and history, to place him - as a tough-minded liberal.
Forget the cautious moderation that often marked his first term and frustrated his most liberal supporters. His second inaugural struck a resolute, even combative tone as Obama positioned himself as a 21st century champion of the disadvantaged, a modern-day heir to the Progressive Era (a period of social activism and political reform in the United States that flourished from the 1890s to the 1920s).
His speech marked the culmination of a theme Obama started claiming more than a year ago when he spoke in the same Kansas town where Theodore Roosevelt a century ago laid out his vision for a new nationalism of government as protector of the poor and working class against the rich and powerful.
Then, it was helping the people survive the sharp edges of the Industrial Revolution at the hands of what Roosevelt once called the "malefactors of great wealth". Now, Obama promises a government to help people make it through an age of rapid social and economic change at the start of a new century.
For a middle class that's been losing ground for a decade, he promised new policies. For gays emerging from the shadows of society, he promised recognition and rights, the first president ever to use the word "gay" in an inaugural address. For immigrants who snuck into the country without documentation, he offered the promise of a new policy.
"We the people," Obama said, "understand that our country cannot succeed when a shrinking few do very well and a growing many barely make it."
He challenged the country to set aside the politics of confrontation in search of progress toward great challenges. "We cannot mistake absolutism for principle, or substitute spectacle for politics, or treat name-calling as reasoned debate," he said. "We must act, knowing that our work will be imperfect."
He also used the speech to forge a bond with the country, signalling that he speaks for and with the people, more than individual members of Congress. He used the phrase "we the people" five times. He used the word "we" more than 60 times.
"We will respond to the threat of climate change, knowing that the failure to do so would betray our children and future generations," Obama vowed.
"We, the people, declare today that the most evident of truths - that all of us are created equal - is the star that guides us still; just as it guided our forebears through Seneca Falls, and Selma, and Stonewall," Obama declared, invoking touchstones of the drives for women's rights, civil rights and gay rights.
Whether the address will translate into policy and better relations is questionable.
The occasionally defiant and often political tenor of his remarks could prove risky. Obama still has to face a Republican Party that controls the House of Representatives and has enough votes to block most Senate legislation.
And he starts his second term with no honeymoon period. Although Obama won re-election with 51.1 per cent of the popular vote, his latest Gallup approval rating was 50 per cent, meaning his coalition is intact but not growing. Large numbers of Americans remain uneasy about their economic futures.
Chances are that his address won't change Washington, at least not immediately.