Condoleezza Rice was the first black female to be appointed as US secretary of state.
She was also the first to occupy the key post of national security adviser.
She is the most academic member of the Bush foreign affairs team and - because of her gender, background and youth - one of the most distinctive.
Personally close to the Bush family she is often invited to spend weekends with the president and his wife Laura at Camp David.
Ms Rice has been one of his key supporters during the wars in Afghanistan and Iraq, and in President Bush's continuing "war on terror".
But while the Iraq war has taken its toll on the president's approval ratings, hers have held steady.
She has consistently been one of the most popular members of the Bush administration and she has been touted to take the Republican ticket in the 2008 presidential elections - despite repeatedly ruling herself out.
Ms Rice was well-known for her stern demeanour as national security adviser - earning her the nickname "warrior princess" - but as secretary of state she has assumed a more genial air.