|Mitchell steered negotiations that led to a peace agreement in Northern Ireland [EPA]
George Mitchell, a retired US senator, served as special envoy to Northern Ireland during the Clinton administration and brokered the landmark Good Friday accord in 1998 that ended decades of bloody violence in the conflict.
However, as US president Barack Obama's special envoy to the Middle East, he arguably faces his biggest challenge yet.
His latest appointment comes in the wake of a three-week Israeli offensive against Hamas fighters which left more than 1,300 Palestinians dead. Thirteen Israelis were killed.
Speaking after accepting the appointment, Mitchell said he did not "underestimate the difficulty" of his assignment.
He is no stranger to Middle East affairs, having chaired a 2001 committee tasked with investigating the events leading up to the second Palestinian intifada, or "uprising" in 2000.
A Maronite Christian son of a Lebanese immigrant mother and a father of Irish descent, Mitchell, 75, has also been an army intelligence officer, a trial lawyer and a federal judge.
In 2000, Bill Clinton, the former US president, asked him to compile a report on the causes of the Israeli-Palestinian conflict, but the Mitchell Report was submitted only after George Bush, the former US president, took office.
Mitchell's report called for the Israelis to freeze construction of new settlements and stop shooting at unarmed demonstrators.
It also called for the Palestinians to prevent attacks and punish those who perpetrated them.
The report's findings eventually became the basis of the so-called road-map to Middle East peace.
A liberal Democrat, he spent 14 years as a US senator representing Maine. He was also majority leader in the US senate, where for six consecutive years his peers voted him its most respected member.
He left the senate in 1995 and declined a nomination to become a Supreme Court judge, but remained active in public life.
In the 1990s Clinton named him special envoy to Northern Ireland, where he was tasked with taming the sectarian violence that had claimed thousands of lives.
In 1998, Mitchell cemented his reputation as a skilled diplomat by brokering talks that resulted in the Good Friday Agreement that led to stopping the long-standing conflict there.
Alistair Crooke, a former EU adviser on the Middle East, told Al Jazeera that Mitchell was "different" from other envoys.
"He is very, very patient and he is extremely good at understanding that it is a choreography of building confidence that is actually the main part of building a peace process," he said.
Crooke said that Mitchell is a person who uses non-confrontational, non-aggressive language and he is a "great listener".
After Northern Ireland, Mitchell chaired an investigation into Salt Lake City's bid for the 2002 Winter Olympic games and in 2007, he led an investigation into steroid use in the US baseball league.
He has already been honoured with the chancellorship of Queen's University, Belfast, and America's highest civilian award - the Medal of Freedom - among others.