He was due to take up the post of first vice-president, a key part of the peace process aimed at ending more than two years of civil war.
Tens of thousands of people have been killed in a war marked by numerous atrocities, with more than two million forced from their homes and nearly six million in need of emergency food aid.
The conflict broke out in December 2013 when President Salva Kiir accused Machar of planning a coup, claims he denied, setting off a cycle of retaliatory killings that divided the desperately poor country along ethnic lines.
Billboards have been erected heralding the return of Machar to take up the post of vice-president – the same job he was sacked from months before the conflict erupted – and forge a unity government with arch-rival Kiir.
“Reconciling, uniting the nation,” read one giant poster on a dusty street, above the smiling faces of Kiir and Machar.
While Machar’s arrival was to be a symbolic step forward, experts warn that implementing the terms of the peace deal will be a long and tough task.
Rival troops inside city
“It will allow the formation of the transitional government, the most significant step in the implementation of the peace agreement,” said Casie Copeland from the International Crisis Group (ICG) think tank, who warned that conflict will likely continue.
Several militia forces, driven by local agendas or revenge, do not obey either Machar’s or Kiir’s commands.
While inside Juba, tensions are high ahead of Machar’s return. A 1,370-strong armed rebel force finished arriving in the city earlier this month as part of an August 2015 peace deal, while government forces say they have pulled out all but 3,420 of their troops, according to the agreement.
Those troops are based in basic camps scattered in and around the capital, while other forces are not allowed within a 25km radius of Juba.
Opposition forces accuse the army of sending truckloads of soldiers back into the city, claims the army denies.
The United Nations has over 11,000 peacekeeping troops in South Sudan, many of them guarding the 185,000 civilians who have spent the past 28 months inside UN bases, too afraid to leave in case they are attacked.
Both the government and rebel sides have been accused of perpetrating ethnic massacres, recruiting and killing children and carrying out widespread rape, torture and forced displacement of populations to “cleanse” areas of their opponents.
‘Armed to the teeth’
“It will require extreme diligence by security forces of the government, the opposition and the UN,” warned veteran journalist Jacob Akol in an editorial for the Gurtong peace project.
“Both sides are armed to the teeth… should fighting break out this time in Juba, we should expect prolonged battles in the city.”
Machar, who last year said it would not be possible to have peace while Kiir remained in power, is due to fly Monday from his rebel base at Pagak in the far east of the country, close to the Ethiopian border, rebel spokesman Colonel Nyarji Roman said.
He is expected to be swiftly sworn in as vice-president at the presidential palace alongside Kiir, but a welcome rally by his supporters may be cancelled amid government security fears.
The swearing in is expected to be attended by African Union representative Alpha Oumar Konare, a former president of Mali, as well as Festus Mogae, a former Botswanan president who heads the international ceasefire monitoring team.
Mogae, who is typically upbeat about developments in the fractured nation, has already warned that the “formation of a new government will not in itself be a panacea”.
Source: Mail & Guardian Africa