For two decades, John Garang personified Sudan's bloody civil war. For the past seven months, he personified peace. His death this weekend will sharply test which legacy will prevail.
Distraught rioters burned cars and threw stones Monday in Khartoum, Sudan's capital. But Sudanese officials were quick to say that Mr. Garang's death - in a helicopter crash blamed on bad weather - would not halt this year's historic progress toward peace.
"We lost Garang at a time when we needed him most, but we think that we have made great strides toward peace and we believe that [the] peace process should continue," said Garang aide Nihal Deng.
The Sudanese government, meanwhile, said the former rebel commander's passing would "gives us more strength" to continue the peace process.
Still, observers say the loss of Garang is a major blow to Africa's largest country, clinging to a fragile peace and still reeling from the humanitarian disaster in Darfur.
After leading the Sudan People's Liberation Army (SPLA) since 1983, the charismatic - and sometimes ruthless - colonel signed a deal with the Arab-dominated northern government in January, ending a 21-year conflict that killed 2 million people. Just three weeks ago, Dr. Garang was sworn in as the country's vice president, working with his former enemy, Sudanese President Omar el-Bashir.
The January agreement was midwifed by the Bush administration and was a high-profile contribution to the overall decline in the number of African wars.
But because the deal was dominated so personally by Garang and his northern counterparts - who negotiated word by word and line by line for years - its success depended largely on the considerable force of Garang's personality and power.
His demise, analysts say, will test whether the impetus for peace is larger than one man. It also removes a powerful moderating influence inside Sudan's government, which was involved in what the US calls genocide in the separate conflict in the country's western Darfur region.
Initially, there were no signs of foul play in the crash, which happened along the Sudan-Uganda border. Yet it comes at a fragile time, because "the peace isn't yet institutionalized," says Richard Cornwell of the Institute for Security Studies in Pretoria, South Africa.
This was a hugely "personal deal" between Garang and Mr. Bashir, he adds. The Sudan conflict began in 1983 when the north tried to impose Islamic sharia law on the Christian and animist south.
As the leadership of Garang's SPLA gathers for an emergency meeting, a major question looms: Who will replace Garang - and will that person be able to persuade the many disparate southern militia groups to stick with the peace deal?
There is deep skepticism among other southern leaders about the wisdom of the deal. It set up a six-year interim period, with confidence-building measures, including the withdrawal of northern troops from the south.
At the end of the six years, southerners will vote on whether to secede from the north. Garang - who got his PhD at Grinnell College in Iowa - was one of the few southerners who preached the value of north-south unity.
"He was well aware that the south could disintegrate into warring factions" if it seceded from the north, Mr. Cornwell explains. North-south unity, Garang calculated, would also help keep the south unified - because it would keep southern groups focused on dealing with the north, not on their own infighting.
It was this kind of political astuteness that gave Garang such clout. "Garang was the one man who could hold the south together," adds Cornwell.
Whoever succeeds Garang must now work with Bashir to confront a major issue behind Sudan's conflicts: Whether the country's outlying regions - the south, Darfur, and the east - will get more power and economic support than they traditionally have had from the central government in Khartoum.
• Material from the Associated Press was used in this report.