Story highlights Arab Spring has changed political make up of Middle East and North Africa

Leaders once seen as "untouchable" have been toppled

Tunisia, Egypt and Libya have all undergone major upheaval

How times change. Less than a year ago, these four men were some of the most powerful in North Africa and the Middle East. Today one is dead, one in exile and another is in jail awaiting trial. Only one of them remains in power.

Tunisia's Zine al-Abidine Ben Ali, Yemen's Ali Abdullah Saleh, Libya's Moammar Gadhafi, and Egypt's Hosni Mubarak were snapped, smiling for the cameras, at a summit of African and Arab leaders held in Gadhafi's hometown, Sirte, last October.

A year on, the Arab Spring uprising has swept through their countries, and the leaders once feared, loathed and seen as untouchable have been swept aside.

Tunisian President Zine al-Abidine Ben Ali was the first of the group to fall. The unrest that would develop into the Arab Spring was sparked in his country in December last year, when fruit seller Muhammad Al Bouazizi set fire to himself in frustration at youth unemployment in the country.

Al Bouazizi died days later, but his actions inspired a mass protest movement, with thousands taking to the streets to demand political change.

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Ben Ali, who had ruled Tunisia since taking power in a coup in 1987, fled to Saudi Arabia three weeks later, on January 14. He was tried in absentia for corruption, and sentenced to 35 years in prison.

Tunisia will hold its first post-revolution elections this weekend.

Hosni Mubarak was the next to lose his grip on power as unrest spread into Egypt and tens of thousands of Egyptians set up a protest camp in Cairo's Tahrir Square.

Hundreds were killed and injured as those calling for Mubarak -- president since 1981 -- to resign and leave the country clashed with pro-government forces.

After initially refusing to hand over the reigns of power, Mubarak finally stepped down on February 11. He is currently on trial for corruption and the killing of more than 800 protesters.

Gadhafi had fled there after rebel fighters took control of the capital, Tripoli two months ago following a months-long battle for towns and cities across the country.

Only one of the four, Yemeni President Ali Abdullah Saleh, is still in charge -- despite widespread unrest in his country, where peaceful protests in Sanaa, Aden and Taiz have met fierce resistance from units of the army still loyal to Saleh, leaving hundreds dead.

Saleh, who has been in power since 1978, survived an assassination attempt in June when the presidential palace was bombed, killing five people and injuring Saleh and several of his ministers.

He spent months in Saudi Arabia receiving medical treatment for burns and a collapsed lung and only returned home last month.

He has repeatedly pledged to step down before the next presidential election but opponents say he has broken such promises many times before.