Myanmar's President Thein Sein, a former general, may go down in history as the man who led "irreversible change".
He made the pledge to the UN General Assembly in New York in 2012, saying Myanmar (also known as Burma) was on a path from which it would not backtrack. His visit to the United States was the first by a Burmese leader in 46 years.
Thein Sein, 67, took office in March 2011, after the country's first election in 20 years in November 2010. Since then, he has led a process of reform in Myanmar, ruled for decades by a military junta of which he was a key member.
Under his administration the government has freed hundreds of prisoners, including political detainees, embarked on peace deals with ethnic minority groups and relaxed media censorship.
He has been welcomed cautiously onto the world stage, despite warnings from critics that many key tests remain for Myanmar's reform process.
This warning was echoed in November 2014 by opposition leader Aung San Suu Kyi, who said that the pace of reform had stalled.
Born in a small village in the delta of the Irrawaddy river, in an area now known as Ngapudaw township, Thein Sein was from a humble background. His parents were farmers, he said.
He graduated with an arts degree from Burma's military academy in 1968 and rose steadily through the ranks in his 40-year career.
He reached the leadership circle in the 1990s when he became a member of the State Peace and Development Council, as the junta called itself at the time.
He was made first secretary of the council after the downfall of former intelligence chief General Khin Nyunt in 2004. Thein Sein also chaired the National Convention, which drafted the country's new constitution.
When the previous prime minister, Soe Win, fell ill, Thein Sein was made acting prime minister in May 2007.
Confirmed in the post in October that year, he became the public face of the regime, representing it at Asean and UN meetings. He served as prime minister for four years.
In April 2010, like many other top junta officials, he swapped military uniform for civilian garb to form a political party.
It was Thein Sein who applied to register the United Solidarity and Development Party (USDP), which dominated the elections in November 2010 and has sweeping control of the parliament.
Analysts said at the time that his appointment was orchestrated by junta leader Than Shwe, who needed an acceptable face to front the country's transition.
"He won't rock the boat," said Aung Zaw, editor of the Thailand-based Irrawaddy magazine, speaking when he took office.
"He is not a fire-breathing dragon, so he doesn't pose any threat to Than Shwe, who will continue to exercise absolute power."
But once he took office, Thein Sein's government began a process of change that surprised his critics.
He met freed pro-democracy leader Aung San Suu Kyi, who subsequently chose to bring her NLD party back into the political process, having boycotted the November polls.
The NLD contested by-elections which were deemed by observers to be largely free and fair.
Over the years since her release Thein Sein appears to have developed a good working relationship with Ms Suu Kyi. Media reports made much of the fact that he met her, congratulated her on receiving the US Congressional Medal of Honor and referred to her as a Nobel laureate publicly.
Known to be quiet by nature, Thein Sein has engaged more with international media. He began a steady push for the West to lift sanctions, something he said was a necessity for democracy to thrive and the lives of Myanmar's people to improve.
"There is a quiet determination to him, he is quiet and soft-spoken but will not flinch from a question posed to him," Vijay Nambiar, the UN's top adviser on Myanmar, told Bloomberg.
Asked in a BBC interview whether he was afraid he would be swept away by the winds of change like Mikhail Gorbachev after the fall of the Soviet Union, Thein Sein answered: "I would like to say that Gorbachev and I are not alike, I tell you that.
''We are not making reforms because I want to. We are merely responding to the people's desire for reform. Therefore my future depends on the people and their wishes."
But he was clear that the military would always have a key role in politics. He also made no apology for its past actions, such as imprisoning dissidents and activists.
"They were acting on their beliefs and we were acting on our beliefs," he said. "Everyone was working for the country in their own way."