Mr Powell was critical of President Bush after he left the administration
Throughout the Bush administration's first term in office, Colin Powell was regarded as a moderate voice on several issues, notably on Iraq.
He was also one of the most popular figures in the administration internationally and among Americans.
However, the views of right-wingers such as Vice-President Dick Cheney and Deputy Defence Secretary Paul Wolfowitz more often than not won the day.
As the administration expressed alarm over Baghdad's arsenal in 2002, the secretary of state urged caution and at times seemed at odds with his cabinet colleagues.
Mr Cheney and Mr Rumsfeld argued for early military intervention, but Mr Powell called for United Nations weapons inspections as a "first step", to assess Iraq's weapons industry.
His views in favour of involving the UN and giving Iraq "one last chance" to disarm eventually prevailed.
But Mr Powell - a retired army general - was never afraid of using force during his career.
Born in 1937 in New York's Bronx district to Jamaican immigrant parents, Colin Powell's first tour of duty as a young soldier was Vietnam.
He was regarded by many as a lifelong soldier.
This is the man who, with General Norman Schwarzkopf, led the Gulf War coalition to victory against Iraq in 1991 under George Bush senior, becoming a national hero in the US.
Mr Powell was then chairman of the joint chiefs of staff - the highest military position in the US.
Born in the New York Bronx to Jamaican parents
Served two tours of duty in Vietnam
Served as national security adviser to President Reagan
Retired from military in 1993
Encouraged to stand for president in late 1990s
Became first African-American secretary of state in 2001
He was a professional soldier for 35 years, and throughout his career argued for a strong national defence.
He was national security adviser to President Ronald Reagan in the 1980s and supported the "Star Wars" missile programme.
When he became secretary of state in 2001, Mr Powell became the highest-ranking African-American in any US administration.
He said he wanted to inspire other African-Americans and seems to have succeeded, admired by many for his warmth and geniality as well as his military and political career.
He was consistently the most popular cabinet member in President George W Bush's first term.
Mr Powell's vast military experience helped shape the so-called Powell doctrine of exercising caution when sending US troops to fight abroad.
Under the doctrine, troops should be sent into conflict only where there is a clear national interest and an exit strategy.
The doctrine says troops should be sent in overwhelming numbers or not at all - and only when success is assured.
Reflecting on his experiences of the Vietnam War, Mr Powell wrote in his 1995 memoirs: "When we go to war, we should have a purpose that our people understand and support.
"We should mobilise the country's resources to fulfil that mission and we should go on to win."
Mr Powell himself played down rumours that policy on Iraq had caused a major split in the Bush administration.
In September 2002 he told reporters: "I think there are lots of differences - some are real, some are perceived and some are over-hyped."
The point was, he said, that the government was working hard to find a consensus.
He returned to private life after the 2004 presidential election, and became an increasingly vocal critic of the Bush administration.
He campaigned against the appointment of former Pentagon official John Bolton as Ambassador to the UN, was damning about the federal response to Hurricane Katrina and sided with moderate Republicans against the White House on the issue of detainee rights in Guantanamo Bay.
During the 2008 presidential race, in mid-October, Mr Powell endorsed the Democratic contender, Barack Obama.
He said Mr Obama had "met the standard" to lead "because of his ability to inspire, because of the inclusive nature of his campaign, because he is reaching out all across America".