In six months, the war of attrition between army chief Abdel Fattah al-Burhan and his former deputy Mohamed Hamdan Daglo, who commands the paramilitary Rapid Support Forces (RSF), has killed more than 9,000 people and displaced nearly six million.
Despite the carnage, neither side has managed to seize a decisive advantage.
In Khartoum, the air force has failed to dislodge the RSF, which still controls the capital's streets while the army holds the country's east.
On Thursday, peace talks resumed in the Saudi city of Jeddah, which Riyadh and Washington said Sunday were aimed only at securing a ceasefire deal and the delivery of humanitarian aid.
"The talks will not address broader political issues," statements from both the Saudi foreign ministry and the US State Department added.
To break the stalemate at the exact moment negotiations restarted, the RSF claimed it had captured Nyala, the South Darfur state capital and the largest city in the massive western region of Darfur -- the RSF's traditional stronghold.
With much of Sudan's already fragile infrastructure destroyed in the war, Nyala — with an airport, railway and a key highway intersection -- could be essential for resupplying forces in the area.
The paramilitaries have held the Om Dafouq border post with the Central African Republic for the past three months and have reportedly taken control of additional supply routes to Khartoum, 1,000 kilometers (620 miles) to the northeast.
Nyala is also "the largest military centre in the three states of South Darfur, Central Darfur and East Darfur," a former army officer told AFP, requesting anonymity because he was not authorized to speak to the media.
In taking the city, the RSF would cement its hold on Darfur, where ethnically motivated killings by the RSF and allied militia have triggered a new probe by the International Criminal Court.
The ICC has since the 2000s been investigating war crimes, crimes against humanity and genocide in Darfur, committed by the forerunner of the RSF, the Janjaweed militia.
Beyond its military strategic importance, Nyala is also the economic heart of Darfur -- a region the size of France that is home to around a quarter of Sudan's 48 million people.
The city "has economic ties with Chad, the Central African Republic and South Sudan, extending even as far as Cameroon and the Democratic Republic of the Congo" which has a consulate in the city, local journalist Ezzeldin Dahab told AFP.
On Thursday, as representatives from both sides met with US and Saudi mediators in Jeddah, the RSF released footage of Daglo's brother and deputy Abdelrahim Daglo — on whom the United States has imposed sanctions -- leading troops into Nyala.
The paramilitary force immediately announced the city and its army infantry division had fallen.
However, the army responded that the 16th infantry division had repelled the attack and inflicted "heavy human and material losses" on the enemy.
According to residents, the RSF fighters have spread out across the city.
"RSF fighters are deployed everywhere and we haven't seen the army since Wednesday," resident Adam told AFP from the Al-Wadi neighborhood, asking to be identified only by his first name for fear of reprisal.
Ali, who lives in another district of Nyala, said the two forces had held different parts of the city since the war began, and that the RSF "takeover was done in stages."
After months of skirmishes, the latest stage came last week, when "the RSF attacked the 16th division with 300 armored vehicles," an army source told AFP.
Previous US and Saudi attempts to mediate in the war yielded only brief truces, and those were systematically violated.
Analysts said they believed Burhan and Dagalo had opted instead to wage a war of attrition, seeking to extract greater concessions at the negotiating table later.