Donald H Rumsfeld, at the acme of his career, remained manacled by the ruinous politics of the Iraq war, a man regarded by colleagues as equally smart and combative, patriotic and politically cunning.

At 88, when he died, Rumsfeld had held salient positions in the government under four Presidents and nearly a quarter century in corporate America.

He was two-time defence secretary and one-time presidential candidate.

“Rummy,” as he was often called, was ambitious, witty, engaging and capable of great personal warmth. But he irritated many with his confrontational style.

A man seemingly always in a hurry, he would let loose with a daily flurry of memos to aides — some well down the bureaucratic chain — which he dictated into an audio recorder and were typed up by assistant. They became known as his “snowflakes.”

An accomplished wrestler in college, Rumsfeld relished verbal sparring and elevated it to an art form; a biting humor was a favourite weapon.

Still, he built a network of loyalists who admired his work ethic, intelligence and impatience with all who failed to share his sense of urgency.

An associate of President Richard Nixon, Bryce Harlow, who helped persuade Rumsfeld to resign from Congress and join the Nixon Cabinet as director of the Office of Economic Opportunity in 1969, called him “rough and ready, willing to tangle” and “the kind of guy who would walk on a blue flame to get a job done.”

Rumsfeld is the only person to serve twice as Pentagon chief. The first time, in 1975-77, he was the youngest ever. The next time, in 2001-06, he was the oldest.

He made a brief run for the 1988 Republican presidential nomination, a spectacular flop, unusual for a man who walked the corridors of power including as White House chief of staff, US ambassador and member of Congress.

For all Rumsfeld’s achievements, it was the setbacks in Iraq in the twilight of his career that will likely etch the most vivid features of his legacy.

By the time he arrived at the Pentagon in January 2001 for his second stint as defense secretary, the military that Rumsfeld inherited was in a slow-motion transition from the Cold War era to a period dominated by ethnic conflicts in the Balkans, humanitarian crises in the Horn of Africa and spasms of terrorism. Among the other prominent worries: China’s military buildup and the nuclear ambitions of Iran and North Korea.

But nine months into his tenure, on 11 September, Rumsfeld found himself literally face-to-face with the threat that would consume the remaining years of his tenure. When a hijacked American Airlines jetliner slammed into the Pentagon, Rumsfeld was in his third-floor office meeting with nine House members. He later recalled that at the instant of impact, the small wood table at which they were working trembled.

Rumsfeld was among the first to reach the smoldering crash site, and he helped carry the wounded in stretchers before returning to his duties inside the building.

The nation suddenly was at war.

US forces invaded Afghanistan on 7 October, and with Rumsfeld at the Pentagon helm the Taliban regime was toppled within weeks. Frequently presiding at televised briefings on the war, Rumsfeld became something of a TV star, admired for his plain-spokenness.

Within months of that success, President George W. Bush’s attention shifted to Iraq, which played no role in the 11 September attacks. Rumsfeld and others in the administration asserted that Iraqi President Saddam Hussein was armed with nuclear, biological or chemical weapons, and that the US could not afford the risk of Saddam one day providing some of those arms to al-Qaida or other terrorist groups.

The US invaded Iraq in March 2003. Critics faulted Rumsfeld for dismissing the public assessment of the Army’s top general, Eric Shinseki, that several hundred thousand allied troops would be needed to stabilize Iraq.

In his 2009 biography of Rumsfeld, author Bradley Graham wrote that it was “both incorrect and unfair to heap singular blame” on Rumsfeld for Iraq.

“But much of what befell Rumsfeld resulted from his own behavior,” Graham wrote in “By His Own Rules.”

Bush on Wednesday hailed Rumsfeld’s “steady service as a wartime secretary of defense – a duty he carried out with strength, skill, and honor.”

In his 2011 memoir, “Known and Unknown,” Rumsfeld offered no hint of regret about Iraq, but acknowledged that its future remained in doubt.

Rumsfeld twice offered his resignation to Bush in 2004 amid disclosures that US troops had abused detainees at Iraq’s Abu Ghraib prison – an episode he later referred to as his darkest hour as defense secretary.

Defiant to the end, Rumsfeld expressed no regrets in his farewell ceremony, at which point the US death toll in Iraq had surpassed 2,900. The count would eventually exceed 4,400.

Born in Chicago as the second child of George and Jeannette Rumsfeld, Rumsfeld wrote in his memoir that he and his father shared a favorite sports team: the Chicago Bears of the National Football League. He recalled that while listening to a Bears game on the radio at home one Sunday in 1941, the announcer interrupted the broadcast to announce that Japanese airplanes had launched a surprise attack on Hawaii.

Rumsfeld was 9 years old.

After Pearl Harbor, Rumsfeld’s father joined the Navy at age 38 and the family moved frequently to be near him on the West Coast.

In high school he met his future wife, Joyce Pierson. In June 1954, Rumsfeld graduated and was commissioned an ensign in the Navy. Six months later he married Joyce.

He launched his Washington career in 1957 by signing up as an assistant to Rep. Dave Dennison, R-Ohio. Soon he was serving as a congressman himself, first elected to represent Illinois in 1962. He served four terms.

One of his early acts as a member of the Nixon White House was to hire a young Dick Cheney, starting a lifelong friendship.

Rumsfeld was working as the US ambassador to NATO in Brussels, Belgium, when he was recalled to Washington to lead President Gerald Ford’s transition team after Nixon resigned in August 1974. He became the new president’s chief of staff and then, in November 1975, his defense secretary.

After leaving the Pentagon in 1977, Rumsfeld embarked on a successful business career in the private sector, including as chief executive officer, president and then chairman of G.D. Searle & Co., a major prescription drug manufacturer.

Two decades later, Rumsfeld was again dealing with Saddam – this time overseeing an invasion that toppled the tyrant and led, ironically, to Rumsfeld’s own downfall.

He is survived by his wife, Joyce, three children and grandchildren.