On 12 March, at a specially convened meeting in Cairo, the Arab League voted to recommend to the United Nations Security Council that a no-fly zone be imposed over Libya. Earlier that day, on a military plane flying out of Bahrain, the US defence secretary, Robert Gates, had told reporters that, although the US had the wherewithal to enforce such a policy, "The question is whether it's a wise thing to do and that's the discussion that's going on at a political level."
Presumably, Gates was speaking for the Obama administration. Yet, by the evening of 15 March, any misgivings the president might have had about a no-fly zone appeared to have gone and he was instructing the US ambassador to the UN, Susan Rice, to argue for a resolution responding to the Arab League's call. What changed? Who or what had convinced Obama to, as one writer put it, "pivot on a dime"?
The final decision to press for a UN resolution was taken at a meeting at the White House on 15 March, described by administration officials as "highly contentious". Those responsible for persuading the president of the merits of intervention included the US secretary of state, Hillary Clinton, who participated by telephone from the Middle East, Rice and Samantha Power, the 40-year-old senior director for multilateral affairs at the National Security Council (NSC) and former executive director of the Carr Centre for Human Rights Policy at Harvard University's Kennedy School of Government. Gates and other members of the NSC had argued against.
The irony of being outmanoeuvred by these three "Valkyries of foreign affairs" (a description coined by the writer Jacob Heilbrunn) will not have been lost on Gates. He won't have forgotten what has come to be known as "Monstergate", an episode that occurred in 2008 during the race for the Democratic presidential nomination. Power - who was working as an adviser on foreign policy to Barack Obama, then a federal senator - had taken time out from the campaign to promote her latest book, a biography of Sergio Vieira de Mello, the UN diplomat killed in a bombing in Baghdad in the early days of the US occupation of Iraq. In early March 2008, her publicity tour took her to London where she gave several interviews, including, fatefully, one to the Scotsman newspaper. Asked about negative campaigning by Obama's main opponent in the primary race, Clinton, Power said: "She is a monster - that is off the record - she is stooping to anything." Despite her desperate attempts to retract the remark, the Scotsman published it. She resigned from the Obama campaign soon afterwards.
Power, who was born in Ireland in 1970 and moved with her family to the United States at the age of nine, first met Obama in 2005, when he was newly installed in the US Senate. He had just read her first book, "A Problem from Hell": America and the Age of Genocide (2002), and asked if they could meet to discuss it.
“We were supposed to meet for only an hour," she told the online magazine Salon, "but ended up meeting for three or four hours at a steakhouse. Suddenly, it was almost midnight and I heard myself saying to him, 'Why don't I just quit my job at Harvard and work in your office for a year or whatever?'" Power did just that, taking a sabbatical from Harvard University in 2005-2006. (She was the founding executive director of the Carr Centre there between 1998 and 2002.)
The phrase "a problem from hell" was taken from the late Warren Christopher's description of the war in the former Yugoslavia in the early 1990s. The book grew out of Power's reporting from the Balkans between 1993 and 1996, when she wrote for the Boston Globe and the Economist. Frustrated and enraged by Washington's failure to act in the summer of 1995, when General Ratko Mladic's Bosnian Serb forces threatened the UN "safe area" of Srebrenica, she decided to explore "America's responses to previous cases of mass slaughter".
The book, which won a Pulitzer prize, examines several cases of US inaction in the face of genocide: in Cambodia in the late 1970s, in Iraqi Kurdistan in the 1980s, in the Balkans in the early 1990s and in Rwanda in 1994.
It has two heroes: Raphael Lemkin, the Polish international lawyer who invented the term "genocide" at the end of the Second World War and helped to secure, in 1951, the passage of the UN Convention on the Prevention and Punishment of the Crime of Genocide; and the Democratic Party senator William Proxmire, who, between 1967 and 1986, made 3,211 speeches on the floor of the Senate, urging that the US ratify the convention.
“A Problem from Hell" ends with Power arguing that the US has a "moral responsibility" to stop genocide wherever and whenever it occurs. "When innocent life is being taken on such a scale," she writes, "and the United States has the power to stop the killing at reasonable risk, it has a duty to act."
As she said later: "Genocide was the lens for me." In making policy over Libya, however, that may turn out to be a distorting optic. For all Muammar al-Gaddafi's attacks on civilians and his lurid threats of further reprisals against the rebels, there is no genocide taking place in Libya. As the political philosopher Michael Walzer - who, like Power, supported humanitarian intervention in the Balkans - has pointed out, there is a difference between stopping a massacre and overthrowing a tyrant. One lesson we ought to have learned from the Iraq war is that the latter has to be "local work".
Jonathan Derbyshire is culture editor of the New Statesman