Mohamed ElBaradei, a former head of the UN nuclear watchdog and a Nobel peace laureate, resigned after just weeks in office as Egypt's vice president for foreign affairs following a deadly police crackdown on supporters of deposed president Mohamed Morsi.
"I had hoped the rise of the people on June 30th could bring the country to back its normal course towards realising the goals of the revolution," he wrote, referring to mass anti-Morsi protests on that date.
"[This] caused me to heed the call of patriotic forces to take part in the rule; however, the course has been deviated from, reaching this state of polarisation and grave division, and the social fabric is threatened as violence breeds violence," he added.
It was a sharp turnaround from weeks earlier, when, in an interview with the New York Times in early July, he defended Morsi's ouster.
"We did not have a recall process," ElBaradei said. "People ask for the recall process with their feet in Tahrir Square. In my judgment, we could not have waited even one more week.”
Two years ago he was tasked by several opposition movements including the Muslim Brotherhood to negotiate with the Hosni Mubarak government. But now he stands opposed to Morsi of the Muslim Brotherhood, saying Morsi has "failed" in leading the nation towards a proper democratic path after the 2011 uprising.
On June 29, the 71-year-old ElBaradei released a video message saying, "The current revolution has erupted so that each one of us lives as human and be treated like human".
ElBaradei already enjoys the strong backing of the June 30 Front, an amalgam of several groups opposing Morsi who believe ElBaradei is "the voice of their demands".
On July 2, the Front - created by the Tamarod ("Rebel") campaign for the purpose of organising mass protests - tasked ElBaradei to speak with the Brotherhood on its behalf. The Front’s statement said he was chosen to avoid any fragmentation among the opposition.
ElBaradei left Egypt 30 years ago to work for the United Nations. He returned to Cairo in 2010 after resigning from the International Atomic Energy Association (IAEA), receiving an exuberant welcome from supporters who hoped he would stir up Egyptian politics by running for president. Days after retiring from the IAEA, ElBaradei said a decision on entering the 2011 presidential race would depend on guarantees of a fair election.
ElBaradei is widely respected in Egypt and has received the country's highest honour, the Nile Shas, in 2006.
He was born on June 17, 1942, in Cairo, where his attorney father headed the bar association, a position that sometimes put him at odds with then president Gamal Abdel Nasser. Following in his father's footsteps, ElBaradei earned his law degree at the University of Cairo in 1962.
"My father taught me that you have to stand by your principles. He was president of the bar association and was preaching civil liberties and human rights during some of the most repressive years of the Nasser era. I think that's a lesson I remember from him... That you stand up for what you believe in," ElBaradei has said.
Two years after obtaining his law degree, ElBaradei joined the diplomatic service, and was assigned to the Egyptian missions to Geneva and New York, where he earned a doctorate in international law and later taught. He has written that his New York years were among the most formative, helping him to broaden his world view.
Camp David negotiator
As special assistant to the Egyptian foreign minister, ElBaradei served on the negotiating team at the historic Camp David peace talks that led to Egypt's peace treaty and diplomatic relations with Israel.
He began his UN career in 1980, and was sent to Iraq in the wake of the 1991 Gulf war to dismantle Saddam's nuclear programme.
In 1997, he was chosen as head of the IAEA, a role that made him an international household name and led to confrontations with Washington, first over Iraq and later over Iran. When the US claimed that Iraq was buying uranium in Africa, ElBaradei dismissed the evidence before the UN Security Council as fake.
Though he angered Washington by challenging claims that Saddam Hussein was hiding a secret nuclear programme, he was proved right when no nuclear weapons were found after the 2003 US invasion.
In 2005, ElBaradei and the IAEA were awarded the Nobel Peace Prize for their efforts "to prevent nuclear energy for being used for military purposes and to ensure that nuclear energy for peaceful purposes is used in the safest possible way".
He is married to Aida Elkachef, a kindergarten teacher, and has two children, Laila and Mostafa.