In 2002, as chairman of the Senate Foreign Relations Committee, Biden gave his blessing to the use of force the following year by then president George W. Bush who falsely asserted that dictator Saddam Hussein had weapons of mass destruction.

For nearly 20 years since, Biden has been explaining himself, facing criticism during the 2020 election campaign both from Bernie Sanders, his leftist rival for the Democratic nomination, and incumbent Donald Trump, who broke with most Republicans by denouncing "forever wars."

And every time, Biden, now 78, took pains to make amends.

"I did make a bad judgment," Biden said at a July 2019 debate.

But Biden insisted he opposed the war and believed that Bush wanted the war authorization to pressure Saddam to let in weapons inspectors.

The historical record reads differently. In mid-2003, Biden said that Bush "has stated his determination to remove Saddam from power" and said he still believed he made the "correct" vote.

Biden's record on war has never been entirely consistent. He voted against the first Gulf War in 1990 that forced Iraqi forces out of Kuwait.

But a key factor in his shift of thinking came when his cherished son Beau deployed to Iraq, with Biden thinking not only as a senior policymaker but as a father.

In his speech Wednesday from the White House, Biden said that Beau's service had been his "North star" in deciding on Afghanistan -- and recalled that some soldiers deployed in Afghanistan were not even born on September 11, 2001.

By the time he became Barack Obama's vice president, a very different Biden had emerged.

He forcefully pleaded for a complete pullout of troops from Iraq, which Obama ordered in 2011.

"I was responsible for getting 150,000 combat troops out of Iraq -- my son was one of them," he said in a presidential primary debate.

While many have described the 2003 invasion of Iraq as a historic blunder by the United States, the 2011 withdrawal has also come under fire by critics who say it led to a vacuum that allowed the rise of the ultra-violent Islamic State extremist movement.

- Critical voice on Afghanistan -

Like the vast majority of Americans, Biden backed the 2001 invasion of Afghanistan to root out the Tailban and Al-Qaeda after the devastation of the September 11 attacks.

But Biden became the most persistent voice inside the Obama administration calling for an exit in Afghanistan.

His concerns date from his time as a senator when he reportedly stormed out of a dinner in Kabul with then president Hamid Karzai whom Biden felt was giving short shrift to legitimate US concerns on corruption.

Unlike on Iraq, Biden did not prevail on Afghanistan, with Obama embracing a "surge" of troops for the "good war" on Afghanistan. By 2011, an all-time high of 100,000 US troops were in Afghanistan.

Biden's hesitation extended to the operation to kill Osama bin Laden, with the vice president counseling against the high-risk raid into Pakistan. Obama went ahead with the raid, killing the world's most wanted man and mastermind of September 11.

Richard Holbrooke, the veteran envoy who was in charge of Afghanistan and Pakistan at the start of Obama's presidency, recounted a harsh exchange with Biden in his diary, later included in a biography of the late diplomat by George Packer.

Holbrooke, according to his diary account, agreed with Biden that the Afghanistan war was unwinnable but argued that the United States should not abandon the gains made.

Biden rose from his chair in anger. "I am not sending my boy back there to risk his life on behalf of women's rights!" Biden was quoted as saying.

"It just won't work, that's not what they're there for."