By Peter Biles
BBC World Affairs correspondent
Under Meles Zenawi's leadership, Ethiopia has undergone dramatic change since 1991.
Mr Meles took part in the guerrilla campaign against the Mengistu regime
A political system, based on ethnic federalism, has replaced the centralised rule that existed during the years of the feared Mengistu dictatorship.
However, the protests that have erupted in the wake of the May 15 elections present Mr Meles with one of the most serious challenges of his premiership.
And he will now have to deal with strong opposition parties for the first time.
The Ethiopian government may point to the fact that there was no freedom of expression whatsoever during Mengistu's rule, but a heavy-handed reaction from Mr Meles' security forces to public demonstrations in Addis Ababa is certain to be viewed as another blow to Africa's so-called "renaissance".
Meles Zenawi can reflect on the fact that he's now been in power as long as the man he helped to overthrow - Colonel Mengistu Haile Mariam.
In May 1991, the rebels of Ethiopian People's Revolutionary Democratic Front (EPRDF) swept down from the Tigrayan highlands and entered Addis Ababa, as Mengistu's demoralised forces melted away.
Mr Meles, then EPRDF chairman, arrived in the capital a few days later. Although a relatively unknown public figure at that time, he was no stranger to Addis Ababa.
Life is hard for many Ethiopians
Mr Meles had completed his schooling at the General Wingate School in 1972, and then entered the medical faculty of Addis Ababa University.
But in 1974, he left to join the Tigray People's Liberation Front (TPLF) at the start of its armed struggle against the Derg (military junta).
In the 1980s, the TPLF had a reputation as hard-line communists who saw Enver Hoxha's Albania as a model state.
Observers used to joke that when the TPLF captured towns from Mengistu's Marxist regime, they would take down the ubiquitous portraits of Marx, Engels and Lenin in government offices, and replace them with even larger ones.
Since 1991, the TPLF has remained the leading party in the ruling EPRDF coalition, and the Marxist-Leninist ideology of the Cold War era has given way to economic liberalisation.
Early in his premiership, Meles Zenawi was regarded as one of a breed of younger African leaders who would spearhead a new beginning on the continent.
So too was his Eritrean counterpart, Isaias Afewerki. The two men are said to be distant relatives, and although Mr Meles hails from Adwa in northern Ethiopia, his mother was from Adi Quala, across the border in Eritrea.
Together, their respective rebel movements had fought Mengistu, and in 1993, Mr Meles' government in Ethiopia did not oppose Eritrea's independence, even though Ethiopia became a landlocked nation as a result.
However, the unexpected war between Ethiopia and Eritrea (1998-2000) destroyed the relationship between Mr Meles and Mr Isaias. These days, the two leaders are no longer on speaking terms.
In Addis Ababa during the launch of the Commission for Africa report in March 2005, I asked Mr Meles whether he could finally settle the border dispute with Eritrea.
"We believe the problem between ourselves and Eritrea will have to be resolved through dialogue", he said.
"We have tried in the past, but it takes two to tango". Eritrea however, argues that Ethiopia is still blocking the implementation of the international boundary commission's ruling.
In 2001, a year after the war ended, Mr Meles faced a power struggle within the TPLF.
Several senior members of the Central Committee opposed some of Mr Meles' more progressive reforms, and also accused him of being "too soft" on Eritrea.
Mr Meles narrowly survived and began to develop a new power base. As leader of the biggest and most powerful country in the Horn of Africa, it has been easy for him to forge close alliances with the West, particularly in the light of US concerns about the War on Terror.
In the last 12 months, Mr Meles has also enjoyed the favoured status of being one of the members of Tony Blair's Commission for Africa, which has brought poverty reduction to the fore. This is something that has irritated the political leadership in Eritrea.
The real test for Meles Zenawi, though, is to demonstrate that Ethiopia is genuinely committed to the freedom and democracy that it espouses, and at a time when calls for good governance are high on the international agenda.