Ursula von der Leyen, Germany's first female defence minister, is a worldly and ambitious trained physician and mother of seven seen as a budding possible successor to Chancellor Angela Merkel.

With political star power and appeal especially for women voters, she has been a campaign asset for Merkel, but also a potential rival who has shown she is not scared to challenge the powerful leader.

Brussels-born, fluent in English and French, with a degree from the London School of Economics, she has cultivated a network of contacts on both sides of the Atlantic.

Most recently she toured European capitals with a drive to help Europe's jobless youths, as labour and social affairs minister.

Unlike the reserved and cautious Merkel, von der Leyen is not averse to taking the occasional political risk, prone to flash a winning smile even when it backfires.

The sharpest criticism of von der Leyen, 55, has been of her best-in-class style, of the super-mum who juggles family and work duties with discipline and a perfect hairdo in a way some voters and colleagues say they find slightly unnerving.

Often dubbed "the soloist" for her go-it-alone style, the political late-bloomer lacks a strong base within her conservative CDU, which she joined in her thirties only to breeze past many old-timers.

She is credited with driving social reforms, many borrowed from the centre-left opposition, including expanding child care and granting new fathers paid leave -- steps that helped modernise the image of her party.

Ursula von der Leyen was born on October 8, 1958 in Brussels into a venerable political family.

As the daughter of Ernst Albrecht, the former CDU state premier of Lower Saxony, she spent her late teenage years under police protection at a time when left-wing extremists were targeting political and business figures.

The threat, which has never been publicly spelt out, even forced her to move to London to live in an uncle's flat under the assumed name of Rose Ladson, and kept a security detail at her side well into adulthood.

A top-grade student, she studied economics then medicine, going on to work in a women's clinic. She interrupted her career to be a housewife when her husband, a professor of medicine, won a scholarship to Stanford.

She only joined the CDU at age 32 and entered the Lower Saxony parliament a decade ago, going on to win her first Bundestag seat in 2009 when Merkel made her family affairs minister.

Von der Leyen -- who once said she may have ended up in the ecologist Greens party were it not for her father -- has remained an outsider in the traditionally conservative and male-dominated CDU.

In a gamble this year, she broke party ranks to push for a women's quota in corporate boardrooms, citing her personal conviction. The challenge was risky, given Merkel's penchant for axing troublesome rivals.

In the end, von der Leyen agreed to a deal in which a parliamentary vote was scrapped but the CDU promised to support a quota in future. It is now set to become law under the incoming 'grand coalition' government.

At the time, von der Leyen had angered much of her party with her apparent disloyalty -- yet despite her defeat she looked like a winner, having challenged Merkel and survived.

Her nomination to defence minister suggests the chancellor has forgiven her and, some commentators believe, may even see her as a potential successor.

"With this appointment, she has definitively manoeuvered herself within the CDU into the role of the crown princess," news website Spiegel online wrote Sunday.