Robert Gates, the 63-year-old career intelligence officer chosen to replace Donald Rumsfeld at the Pentagon, takes over with the clearest of missions: get American troops out of Iraq as quickly and cleanly as possible.

Mr Gates was, subject to Congressional approval, propelled into the top ranks of the Bush Administration today as Secretary of Defence only hours after voters handed President Bush what he agreed himself was a "thumping" in mid-term elections.

The deeply unpopular Mr Rumsfeld, seen by his enemies as a reckless warmonger and attacked even by senior military officers for strategic blunders, was the obvious scapegoat for the electoral meltdown. Since the invasion of Iraq in March, 2003, more than 2,800 US soldiers have been killed in Iraq.

Although Mr Bush told a White House press conference this afternoon that Mr Rumsfeld's departure should not be taken as a signal that America would be withdrawing from Iraq, he made it clear that the former CIA director had not been chosen as continuity candidate.

The President freely admitted that his Iraq policy was "not working well enough, fast enough" and needed new leadership.

Although Mr Gates is currently serving as president of Texas A&M University, he has been active recently as a member of the Iraq Study Group led by James Baker, the Bush family confidant and former Secretary of State.

That Group has yet to report, but its draft recommendations have been widely leaked and amount to a radical reshaping of US Iraq policy that would have been unthinkable a year ago - including a large reduction of US troop levels and a diplomatic push to engage Iraq's neighbours, including Iran and Syria.

The Group has also pushed for the Iraqi Government to take more responsibility for its own affairs, politically and militarily.

Since those recommendations have not been formally given to the White House, Mr Bush has not had to accept or reject them. But the Administration has noticeably changed its language on Iraq - Mr Bush no longer speaks of "staying the course" for example - and Mr Rumsfeld's departure allows the unthinkable to become policy.

And it would be unthinkable for Mr Bush to appoint his new Pentagon chief from among the group's members if he did not agree with their conclusions.

Born in Wichita, Kansas, in 1943, Mr Gates joined the CIA in 1966 and rose from working-level officer to become its director, also serving as a member of the National Security Council.

He was first nominated as CIA director in 1987 by Ronald Reagan but withdrew amid questions over his and the CIA’s role in the secret sales of arms to Iran and the diversion of profits to Nicaragua’s Contra rebels - the accusation against him being that he hid the truth about the Iran-Contract affair from Congress.

He was nominated again by the first President Bush and led the CIA from 1991 to 1993.

Mr Bush described him today as "a steady, solid leader who can help make the necessary adjustments in our approach to meet our current challenges".

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