When Sudanese protest organisers posted a two-week schedule of demonstrations in late March, there was no mention of a sit-in outside the Defence Ministry in the capital Khartoum.
On April 6 there was a march planned to the sprawling complex to commemorate a popular uprising that toppled an authoritarian regime 34 years ago.
But that evolved into a sit-in that by nightfall had attracted as many as 2 million people, according to some estimates – by far the largest turnout since protests began in December against the rule of autocratic leader Omar Al Bashir.
Five days, about two dozen deaths and hundreds of injuries later, that unplanned sit-in proved to be the final victorious act in Sudan's Arab Spring-like uprising, when on April 11 the military removed Mr Al Bashir, bringing to a close what is perhaps the darkest chapter of Sudan's modern history.
In retrospect, the unexpectedly large turnout outside the military complex offered an opportunity that was too good to pass.
Countless demonstrations during the previous four months attracted relatively modest turnouts in the hundreds or low thousands.
Such protests were unlikely to force the president to step down, even if they had continued for many more months, activists say.
Fatigue and frustration had already begun to creep in after poor response to calls for a general strike in March.
Meanwhile, security forces were increasing their use of force – even beating women in the streets – and detained thousands.
As many as 100 protesters had been killed by early April, although the number could rise significantly by the time a final count is made, activists believe.
Thousands were injured or detained and tortured.
"That's it, Ahmed, we will be ruled by this regime for another 30 years," activist Aseel Abdou, 24, remembers telling her husband in France on the phone in March.
"But then the protest leaders would issue a fiery statement that would rekindle my enthusiasm and we would push on."
The protest leaders understood that only the military could topple Mr Al Bashir's regime. Staging a sit-in outside the Defence Ministry complex seemed like the perfect move.
The area soon became the Sudanese version of Tahrir Square in Egypt's capital Cairo, and the Habib Bourguiba Avenue in Tunis, Tunisia, both of which became household names in the 2011 Arab uprisings.
"It became our zero hour," said Amjad Fareed, spokesman for the Sudanese Professionals Association, an independent umbrella group that led the revolution against Mr Al Bashir.
"It was the time when a critical mass of people were out on the streets, an accumulation of everything we did and worked for since December."
The National spoke to six other prominent activists who took part in the April 6 march and the sit-in that continues to demand that the military hand over power to a civilian administration.
They painted a detailed picture of those historic days, recounting the mixture of fear, hope and euphoria experienced by the protesters, who withstood repeated attacks by troops determined to dislodge them.
They also recounted the critical moments when soldiers and junior officers spontaneously sprang to the defence of protesters, firing at security forces as they approached under the cover of darkness or at snipers positioned on the rooftops of nearby high-rises.
"We screamed and cried for joy when we made it outside the military complex," recalled Mrs Abdou, sipping black coffee in a rickety chair at the sit-in. "It was not easy. We were hit by so much tear gas.
"Still, thousands more kept pouring into the site but not one of the organisers told us what's next."
The first batch of protesters arrived at the site about 1.30pm on April 6, but it was not until 5pm that the Sudanese Professionals Association called for everyone to stay put.
The protesters knew that this was their critical moment and they could not let it pass. But there was one problem: they had no food or water. People posted online calling for deliveries of supplies.
“It was not until around 9pm that several pickup trucks arrived with food and water and everyone settled in," said Mrs Abdou, who spent most of March hiding in Port Sudan, the country's main Red Sea maritime city, to avoid arrest over her activism.
Troops halted their attacks at nightfall but resumed them in the small hours of April 7, starting a pattern that repeated itself over the next five days, in which time activists say 21 people were killed, including five soldiers.
The number of injured is believed to be in the low hundreds.
"They used so much tear gas you could not see anything. Not even right in front of you," said Ahmed Said, 21, an information technology student who now serves as a security volunteer at the sit-in. "The tear gas canisters just kept raining down."
The worst of those days was April 8, when security forces tried to break up the sit-in four times, removing barricades and later firing live rounds, said Alaaeldeen Awad, 38, an activist and surgeon.
Their action drew a heavy response from sympathetic soldiers, who fired back.
"So intense was the firing and the tear gas and stun grenades that the military opened the gates of the complex for us to seek shelter inside," Dr Awad said.
He said that in the middle of the night, security forces in army uniforms approached the flank of the sit-in hoping to drive the protesters away.
But soldiers saw them in their floodlights and scared them off with warning shots. The next night the military would again offer shelter to the protesters.
"We could not sleep at night those days," said Dr Awad, speaking at a field hospital at the sit-in site.
"We tried everything to stay awake. We sang, chanted slogans and banged barricades with metal objects. We screamed at those who dozed off: 'Wake up, this is not a picnic'.
Prominent activist and dentist Ubai El Gazouli, 38, said: "Those young officers and their men tipped the balance in favour of the revolution.
"On April 6, I was marching with others past the security headquarters near the military complex. We expected to be attacked, but military policemen were quick enough to move alongside us to deter the security people from harming us."
The morning of April 11, the day Mr Al Bashir was ousted, was not a peaceful day either, the activists said.
News of his removal started making the rounds at 6am, but the military did not formally announce it until eight hours later.
Security forces, in what appeared to be a desperate bid to break up the sit-in, again attacked, killing two and injuring scores.
For the next three days, sporadic firefights took place between security forces and soldiers, activists said.
The sit-in, now in its fourth week, has since turned into a carnival-like affair, complete with music, dance, face painting and an outdoor market selling mangoes, watermelon and peanuts.
It is a contrast to the anxious and bloody days earlier in April, but politics remains central, with activists delivering fervent speeches from the stage.
And despite overthrowing a dictator after almost 30 years, the activists say their job is not yet complete.
On Tuesday, they fortified the barricades around the site with rocks and bricks and increased searches at the entrances as tension rose between the military and protest representatives over the makeup and powers of the transitional government.
Demonstrators are demanding more civilian oversight in the transition than the military has been willing to concede.
Three rounds of talks have made little progress, with the protest leaders threatening to step up demonstrations to force a civilian transition after accusing the military of trying to cling to power.
And after overcoming so much already, protest organisers say they are ready to continue.
During previous low points, protesters wondered whether it was worth the sacrifices made: lost or disrupted lives, injuries and physical and psychological scars of detention and torture.
But throughout their uprising – the third in Sudan since 1964 – the protesters and their leaders showed ingenuity and creativity, deftly using social media and attracting funds from sympathetic Sudanese expatriates and local businessmen.
The activists said that instrumental to the success of the protests was the involvement of millions of unemployed Sudanese – there are said to be one million out of work in Khartoum – with time on their hands, little to lose and a burning desire for change.
"Not everyone was frustrated or lost heart. The young did not," Dr El Gazouli said.
They even coined a slogan to describe their resolve, he said: "We are the generation that's so strong headed, it will not be ruled by a dancing president".
It alludes to the hallmark shake the former president routinely performed to music while addressing crowds, which was much ridiculed by protesters.
The activists said the uprising might have been long overdue. The genesis of the SPA and the "neighbourhood resistance committees" in Khartoum and elsewhere went back to 2013 protests over food prices, in which at least 300 people were killed.
The latest uprising was also sparked by price rises and shortages, with protesters taking to the streets in cities north and south-east of Khartoum on December 19.
It did not spread to the capital until December 25, when protesters tried to march on Mr Al Bashir's presidential palace to demand he step down.
That march was planned before the start of the unrest outside the capital and its original destination was Parliament. Its demands were increased salaries, not Mr Al Bashir's removal, activists say.
It was the first time that many Sudanese had heard of the SPA, a group whose leaders, organisational structure and membership remain shrouded in secrecy to this day.
"The SPA took on an air of mystery, almost legendary, because no one knew who led it or how it was being run," Dr El Gazouli said.
"The security agencies did not know of its existence, which was a big plus, and the people wanted a body to rally around and lead them. A body that was not politically tainted," said Hadiya Hasaballah, a psychologist and activist.
The SPA issued a weekly schedule for street protests, which while giving the security forces advance notice also allowed protesters time to prepare and mobilise.
"Everyone was so good. When, for example, we said gather at 1pm, everyone showed up on time," Dr Fareed said. "Our war with the security forces was open. There were no secrets."
Many Sudanese protesters credit the organisational skills and discipline of the SPA for much of the revolution’s success. They deftly used social media to organise and mobilise.
When authorities restricted the internet, they used virtual private networks to communicate. When the web went dark, word went out by text message using overseas Sim cards sent by expatriates.
When everything else failed, human couriers delivered news and instructions to neighbourhood resistance committees in the old-fashioned way.
"The SPA showed great management and leadership skills, successfully turning the unrest into a popular uprising that they were able to sustain," said Amal Elzein, a lawyer and a member of the Communist Party's central committee.
"Many of us were tortured in detention to give them the names of the association's leaders. I had not heard of anyone who did."
Mrs Elzein was detained twice during the revolution, including a two-month stint starting on January 1.
Her husband and one of her four children, a 24-year-old university graduate, were also jailed.
"It's a typical bottom-up revolution," Dr El Gazouli said. "It would not be accurate to give all the credit to the association. The real heroes are the children and youths. We could never understand why they were so brave."
Countless clips posted online and apparently filmed at the demonstrations show young protesters picking up tear gas canisters and hurling them back at the security forces, and showing composure when shot at.
During the final days before Mr Al Bashir's fall, young men stood upright next to army troops engaged in gunfights with members of the security forces outside the complex.
One video shows a soldier firing at security forces from a heavy machinegun on the back of a pickup truck before standing on the vehicle's bonnet. A single gunfire shot is heard and he falls to the ground.
To counter the effects of tear gas, donations were used to buy surgical masks and sprays to splash vinegar or yeast diluted in water on the face of affected protesters.
Money was also used to equip first aid stations at protest sites and to pay for surgery for more serious injuries. Funds were also used to compensate families who lost a breadwinner, activists say.
As with the uprisings against military rule in 1964 and 1985, and those in Egypt and Tunisia eight years ago, the protests seemed to bring people together, a sign that could bode well if Sudan is to dismantle Mr Al Bashir's legacy of war, divisions and poverty.
That unity is evident in the sit-in outside the Defence Ministry's complex, where Sudanese from the country's conflict areas – the western region of Darfur, the Blue Nile area south-east of Khartoum and the Nuba Mountains in the south-west – reach out with a spirit of reconciliation that places citizenship ahead of ethnicity or religion.
Of the three regions, Darfur seems to take on added significance given that Mr Al Bashir and several of his aides were indicted by the International Criminal Court in 2010 for genocide there. The UN says that conflict cost 300,000 lives and displaced two million people.
It began in 2003 when ethnic Africans rose up against the government to demand a proportionate share of national resources and an end to discrimination at the hands of Mr Al Bashir and his clique.
A special slogan coined by the protesters and directed at the former president, who is detained at a Khartoum prison, quickly became a rallying cry of the early days of the uprising.
"Oh, you arrogant racist, the whole country is Darfur."