Donald Rumsfeld has died days before his 89th birthday, his family announced today.
Rumsfeld served as Secretary of Defence from 1975 to 1977 under Gerald Ford, and again from January 2001 to December 2006 under George W Bush.
His family paid tribute to the architect of the Iraq war in a brief statement.
"It is with deep sadness that we share the news of the passing of Donald Rumsfeld, an American statesman and devoted husband, father, grandfather and great grandfather," they wrote.
President George W Bush, under whom Rumsfeld served as Pentagon chief, hailed his "steady service as a wartime secretary of defence — a duty he carried out with strength, skill, and honour".
After retiring in 2008 he headed the Rumsfeld Foundation to promote public service and to work with charities that provide services and support for military families and wounded veterans.
Rumsfeld made a brief run for the 1988 Republican presidential nomination, a spectacular flop that he once described as humbling for a man used to success at the highest levels of the government, including stints as White House chief of staff, US ambassador and member of Congress.
For all Rumsfeld's achievements, it was the 2003 invasion of Iraq in the twilight of his career that will likely etch the most vivid features of his legacy.
Following the September 11, 2001, attacks on the World Trade Centre and the Pentagon, Rumsfeld oversaw the US invasion of Afghanistan and the toppling of the Taliban regime. Frequently presiding at televised briefings on the war, Rumsfeld became something of a TV star, applauded for his blunt talk and uncompromising style.
By 2002 the Bush administration's attention shifted to Iraq, which played no role in the September 11 attacks. The war effort in Afghanistan took a back seat to Iraq, opening the way for the Taliban to make a comeback and prevent the US from sealing the success of its initial invasion.
The US-led invasion of Iraq was launched in March 2003. Baghdad fell quickly, but US and allied forces soon became consumed with a violent insurgency.
Rumsfeld twice offered his resignation to Bush in 2004 amid disclosures that US troops had tortured detainees in Iraqi prisons — an episode he later referred to as his darkest hour as defence secretary.
Not until November 2006, after Democrats gained control of Congress by riding a wave of antiwar sentiment, did Bush finally decide Rumsfeld had to go. He left office in December, replaced by Robert Gates.
Rumsfeld is survived by his wife, Joyce, three children and seven grandchildren.