It was Joseph Biden's foreign policy expertise that made him the right man to serve as vice-president of the United States.
Joe Biden is known as a formidable debater
Barack Obama chose the veteran senator as his running mate in the wake of Republican criticism that he was ill-equipped for the role of commander-in-chief.
Mr Biden, a long-time Washington insider, had solid foreign affairs credentials, having chaired the key Senate Foreign Relations Committee three times.
The 65-year-old was also brought on board to help woo the blue-collar white voters who had proved a difficult group for Mr Obama to win over.
The two men complement each other in other ways. While Barack Obama comes across as cool and collected, Mr Biden can be lively and combative in his attacks on opponents.
He says he wants to play an important advisory role as vice-president - but has criticised the broad influence Dick Cheney exercised as deputy to President George W Bush.
"Barack is going to be the guy who makes the policies and makes the decision," he said before the election. "I'll give my best judgement."
Joe Biden was born in 1942 in Scranton, Pennsylvania, one of four children in an Irish-Catholic family.
The family later moved to the small north-east state of Delaware, where Mr Biden attended the University of Delaware and Syracuse Law School.
He has represented Delaware in the US Senate since 1972 and is no stranger to presidential races.
He ran against Barack Obama for the 2008 nomination but dropped out in January.
He also ran for the presidency in 1988 but withdrew after he admitted plagiarising a speech by the then leader of the British Labour Party, Neil Kinnock.
Although he voted to approve the Iraq war, he started warning of the costs of a long occupation of Iraq before it began.
Since then he has advocated a federal solution to the conflict in Iraq, envisaging a loose division of the country along ethnic lines.
His connection to Iraq also has a more personal note. His son, Beau Biden, Delaware's attorney general, is a captain in the Army National Guard, and his unit is set to be deployed to Iraq shortly.
"He'll go… I don't want him going," Mr Biden said recently. "But I don't want my grandsons or granddaughters going back in 15 years. So how we leave makes a big difference."
Mr Biden's reputation as a forceful speaker can be eclipsed by the ability to ask simple questions in a complicated way. And he is prone to the occasional gaffe.
In 2007, he described Barack Obama as "the first mainstream African-American who is articulate and bright and clean and a nice-looking guy".
The two men will now be spending plenty of time together in the White House.
And in his victory speech Barack Obama praised his running mate, calling him "my partner in this journey, a man who campaigned from his heart".