Nearly a year before the world woke up to images of Syrians dying in a chemical weapons attack, Samantha Power was quietly pushing US President Barack Obama for a military strike to stop the "grotesque tactics" of President Bashar al-Assad. For a fleeting moment this month, it seemed she had prevailed.
Now Power, a former senior aide on the US National Security Council and a former war reporter born in Ireland, must negotiate for peace in a new public role as Obama's ambassador to the UN. The president's abrupt decision not to use force in Syria has thrust her into the middle of talks to create a UN Security Council resolution mandating the elimination of Assad's chemical arsenal by the middle of next year.
She will be on the spot this week for her diplomatic debut, as Obama arrives in New York for the UN General Assembly. A woman known for her closeness to the president and the soaring prose of her Pulitzer Prize-winning book on genocide, A Problem From Hell, Power is the lead American negotiator in the difficult, gritty business of arguing with the Russians, Syria's patrons.
Even her supporters wonder if she will be tough enough. US Secretary of State John Kerry will work with her on the resolution, but her performance - in her first weeks on the job - will help to determine America's future course in Syria.
"Most diplomats in a career of 40 years would never get this kind of opportunity to make such a difference at such a critical moment," said Edward Luck, the dean of the school of peace studies at the University of San Diego and a former senior UN adviser on peacekeeping issues. "The stakes could not be higher."
At the UN headquarters last week, Power, who turned 43 on Saturday, looked harried as she swept through the corridors.
"We are determined to have an enforceable and binding resolution," Power said, in the kind of bland, bureaucratic language she might have shunned as a writer for The New Yorker.
One person close to Power said she had been advocating military action in Syria as far back as December of last year.
On assignment for The New Yorker in 2004, Power was among the first to chronicle the bloody ethnic cleansing in Sudan. And as a young freelancer in Bosnia, she reported on the systematic rape of Muslim women.
"Samantha is somebody who believes deeply that American power flows from our values as much as our military might, and that in the world, when we act in accordance with our values, we strengthen our ability to lead," said Anne-Marie Slaughter, a former State Department official.