When Myanmar’s military regime released Aung San Suu Kyi from house arrest, in 2010, she had been the world’s most famous political prisoner for nearly two decades. Within a few weeks, she received a phone call of congratulation from another former political prisoner—Václav Havel, the dissident Czech playwright who, in 1989, had become his country’s first post-Communist leader. The call was the only time they ever spoke directly, but their political relationship had lasted almost as long as her captivity. In 1991, two years into his term as President of Czechoslovakia, Havel had successfully lobbied the Nobel Committee to award its Peace Prize to Suu Kyi in recognition of her leadership of the Burmese pro-democracy movement. When a book of her essays was published, soon afterward, it had an introduction by Havel, who wrote that “she speaks for all of us who search for justice.”

Havel and Suu Kyi were among the many dissidents around the world who, from the mid-eighties to the early nineties, emerged as icons of freedom, often toppling the regimes that had oppressed them. In South Africa, after nearly thirty years in prison, Nelson Mandela negotiated an end to apartheid and then assumed his country’s Presidency. In Warsaw, a shipyard worker named Lech Walesa and a movement called Solidarity swept the Communist government from power. In the Philippines, the dictatorship of Ferdinand Marcos fell after Corazon Aquino, the widow of an assassinated critic of the regime, took up her husband’s struggle. Democratic movements did not always triumph—the Chinese government’s massacre of student protesters near Tiananmen Square is the grimmest example—but, in the last three decades of the century, the number of democracies in the world increased from thirty-one to eighty-one.

Various fates awaited these reformers. Havel and Mandela weathered the inevitable compromises of office with their reputations intact, whereas Walesa, as Poland’s President, became known as an erratic and unreliable leader. But none of them has undergone the kind of unexpected and alarming metamorphosis that Aung San Suu Kyi has. Her moral clarity and graceful bearing long made her a potent symbol of human rights and nonviolence. (There was a 2011 movie based on her life.) But since she became the country’s de-facto leader, in 2016, she has remained impassive in the face of a series of human-rights abuses, most egregiously the brutal oppression of the Rohingya, a Muslim ethnic minority in the west of the country, near the Bangladesh border.

Myanmar is a patchwork of a hundred and thirty-five officially recognized ethnicities, dominated by the Bamar, from the country’s heartland, who make up sixty-eight per cent of the population and most of the ruling élite. Armed conflicts have simmered for decades between numerous ethnic groups and Bamar-led governments. In 1947, Suu Kyi’s father, Aung San, a Bamar general now regarded as the founder of the modern nation, persuaded several groups to put aside their differences in the interest of ending colonial British rule. But he was assassinated shortly before independence, which went into effect in January, 1948, and tribal conflicts soon consumed the young nation.

These civil wars gave the military an excuse to seize power, which it did, in 1962. (It later changed the country’s name from Burma to Myanmar; changed the name of the old capital from Rangoon to Yangon; and built a new capital, Naypyidaw.) The junta ruled ineptly and repressively for nearly fifty years, amid growing pressure for democratic reform. In 2015, when it allowed free elections for the first time in a generation, Suu Kyi’s popularity propelled her party, the National League for Democracy, to a landslide victory. The N.L.D. and the Army cautiously entered a power-sharing agreement and, in 2016, formed a government that is civilian-led but still substantially dominated by the military.

On taking office, Suu Kyi emulated her father by announcing talks to resolve the ethnic struggles. “Our country is thirsty for peace,” she proclaimed. But some conflicts have intensified, and the Army has broken ceasefire agreements. Journalists and activists who are critical of the government have been jailed. Most urgently, the plight of the Rohingya has developed into a humanitarian catastrophe. Attacks on Army and police posts by Rohingya militants last October, and again in August, have unleashed a ferocious crackdown. In the past month, more than four hundred thousand Rohingya refugees have fled across the border into Bangladesh, bringing with them accounts of indiscriminate slaughter and mass rape. Satellite images show that more than two hundred Rohingya villages have been incinerated.

Within Myanmar, the Rohingya are uniquely despised by almost all other ethnicities. Nearly ninety per cent of the country is Buddhist, and most people regard the Muslim Rohingya as illegal immigrants; they are not included in Myanmar’s official tally of ethnicities. Suu Kyi has done nothing to combat this prejudice. Her government has denied visas to a United Nations human-rights team charged with investigating the crisis, and international organizations have been prevented from delivering aid.

The U.N. High Commissioner for Human Rights has called the security crackdown “a textbook example of ethnic cleansing,” and several of Suu Kyi’s fellow Peace Prize laureates, including Desmond Tutu and Malala Yousafzai, have urged her to condemn the violence. Instead, she has described the Rohingya insurgents as “terrorists” and dismissed the worldwide condemnation, saying that international outlets have created “a huge iceberg of misinformation.” Her office has accused the Rohingya of setting fire to their own homes in order to provoke an outcry. In a speech last week, Suu Kyi refused to criticize the Army and offered a sustained exercise in moral equivalence. “There have been allegations and counter-allegations,” she said. “We have to listen to all of them.”

Recently, I travelled to Myanmar and interviewed dozens of people to assess what had gone wrong. Many of them pointed out that Suu Kyi’s power is sharply limited. She has no authority over the Army, while military officers still control key areas of government and have the power to reverse democratic reforms. Some believe that she has made a political calculation not to risk domestic popularity for the sake of a hated and powerless minority; others regard her as lacking political skills. There are also those who think that she shares the Army’s authoritarian reflexes and the anti-Muslim prejudices of the Buddhist Bamar majority. But almost everyone I talked to expressed surprise at the speed and the scale of her transformation. “We never expected that Aung San Suu Kyi would get us this far,” a former student activist and political prisoner who once served as her bodyguard told me. “But, at the same time, we never expected that Aung San Suu Kyi would have changed so much herself once she got into power.”

Aung San Suu Kyi was just two years old when, on July 19, 1947, armed men burst in on a meeting convened to oversee Burma’s transition to independence and killed her father and eight others. Growing up in the shadow of her father’s legend, she was largely shielded from the turmoil of the post-independence years. At the Methodist English High School, in Rangoon, she took classes in morality and geography. Sao Haymar Thaike, a childhood friend and the daughter of Burma’s first post-independence President, told me that Suu Kyi was a serious, bookish girl, raised by a “very strong, kindhearted” mother, Khin Kyi. In 1960, Khin Kyi was appointed Ambassador to India and took her daughter with her. Two years later, Burma’s coup installed a socialist military regime.