Marise Payne once remarked that she became a feminist at age one. It wasn't until she got to university in the 1980s that she realised there were "things ... it was expected a young woman should not or would not do".

She ignored those expectations, she said during a 1996 speech in honour of Robert Nestdale, one of her predecessors as leader of the Young Liberals.

And at 11.30am on Monday, she did something no Australian woman has done, becoming the nation's Defence Minister.

The appointment has been universally applauded, whether by political colleagues or that supposed bastion of blokes the Australian Defence Force.

Indeed there is a veritable glow of satisfaction emanating from Russell, the hillside Canberra suburb where Defence has its offices across the lake from Parliament. Sources there said it was well and truly time to have a female minister.

Senator Payne's fortunes in politics have suffered from being a prominent moderate under solidly conservative prime ministers – first John Howard, then Tony Abbott, though Mr Abbott appointed her human services minister in 2013.

As far back as 1994, she clashed with monarchist and freshly minted Liberal MP Mr Abbott over her decision to join the Australian Republican Movement, which was being led by Malcolm Turnbull.

With Mr Turnbull's ascension at Mr Abbott's expense, the stars have finally aligned for the 51-year-old.

"Marise Payne has been underestimated by too many people for too long," said Brendan Nelson, a former defence minister and Liberal leader.

"Anyone, whether in the defence and security or any other sector of our political and policy class who underestimates Marise Payne does so at their own risk."

Despite arguably being held back in Canberra, she is a powerful figure in the NSW party, keeping the No. 1 Senate ticket spot above the revered Arthur Sinodinos.

She has placed her electorate office in Parramatta and has helped deliver strong results to the Liberals in western Sydney state and federal elections.

Her partner is Stuart Ayres, the NSW Minister for Trade, Tourism and Major Events.

Senator Payne's progressive views have been conspicuous in her 19 years in Parliament. In her first speech to the Senate, she lashed One Nation, lamented the stolen generations, blasted "right-wing media commentators", attacked discrimination against people with HIV/AIDS and called for greater engagement with Asia.

She was among the small clique of Liberal "wets" under Mr Howard who stood their ground against tough border protection measures. And she played a key role in internal opposition to over-reaching aspects of the Howard government's post-September 11 counter-terrorism laws.

However, one key player during that period said  on Monday that Senator Payne was coming more from a classic libertarian perspective than a national security softness that could portend a doveish approach as Defence Minister.

Similarly, Mr Nelson said she would have the right balance of toughness and compassion to be a properly "objective" Defence Minister.

"I think back to the conversations with her when I was minister for defence myself. She was very objective about these things," he said. "There's a sense that because she is on the liberal wing of the party … people might falsely think she'd be less effective … That would be a mistake.

"You don't get to where Marise Payne is going, through everything that she has done in her public and personal life, without being tough. But having said that, she is a person that cares, and … that will translate very much into concern for the troops and their families.

"There's always something strong about appointing a defence minister who has an interest in the area but not an obsession. The latter can be a problem."

Australia Defence Association executive director Neil James, who is not known for mincing his words and certainly not for political correctness, said: "People will try and describe it as a token appointment. She's won this on merit. It's great for the nation."

Senior government sources said there was no concern that she would be too moderate or doveish. Mr Turnbull decided she had simply the right fit of intellect and aptitude.

Whereas her predecessor, Kevin Andrews, had shown scant inclination outside domestic policy areas before being given Defence, Senator Payne had a "deep interest in foreign and security policy", a senior source said.

Mr Turnbull, eager to end the revolving door of defence ministers, was also attracted to the fact that Senator Payne is at the beginning of her ministerial career rather than the end.

The portfolio has too often gone to ministers who had been dumped from something else or had one foot out the door. It is understood the appointment was discussed with Defence brass.

Still, the job won't be easy, Defence being a notoriously strange animal to wrestle with. One insider said all her parliamentary committee work and MP's visits abroad won't have prepared Senator Payne to handle Defence's special internal culture and complexity.

"It's a whole different thing to actually run Defence," the insider said. "It's the strangest, most complex beast in the Commonwealth."

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