In Sudan this week, as the International Criminal Court issued a warrant from the arrest of President Bashir, the BBC's Owen Bennett-Jones found echoes of a 100-year-old conflict.
The sect's leader or sheikh, a frail, blind man was sitting on his bed with his thin legs crossed.
He asked me why I had come. Well, I had heard that his followers met two evenings a week to sing, dance and pray, I said. I was wondering if I could attend a ceremony.
The Mahdi who led a 19th century rebellion is still revered in Sudan
As he contemplated whether or not I could be a problem, he put me straight on one point. "It's not dancing," he said. "That would be against Sharia - it's a moving of the limbs." Then, "Come back at nine."
The men met in a poor suburb of Khartoum in a roughly built brick courtyard with no roof.
Standing in a circle they started to sing the names of Allah. The half moon shone down, offering a gloomy light.
The houses in the area, with doors and windows open to relieve the heat, were packed tightly together.
As I looked into the men's faces I thought this here, right now in the late evening, in a small courtyard on the outskirts of Khartoum is why being a foreign correspondent is such a privilege
As the devotional chants floated through the homes, the prayer leader, resplendent in a gold-edged black robe and with a high white turban, made small hand movements to four drummers instructing them to quicken and slow the pace.
For an hour, the surging rhythms allowed pauses for breath and contemplation, but over time became faster and faster as the men, with some young boys squeezed in between, began to roll their heads from side to side.
And with ever more violent jerks - all the while chanting - they worked themselves into a state of near ecstasy.
Their faces filled with the joyous smiles of religious fervour and then some started dancing - or perhaps I should say moving their limbs - in the middle of the circle.
One tall man with a long white tunic and greying hair, his whole body shaking, moved around the circle of worshippers touching each one, while besides him a five-year-old boy mimicked his every move.
It was about as different to a Church of England service as you could ever imagine.
And as I looked into the men's faces I thought this here, right now in the late evening, in a small courtyard on the outskirts of Khartoum, is why being a foreign correspondent is such a privilege.
I had gone to Sudan to make a history programme. I wanted to learn more about the man who fought the British in the 1880s - a boat builder's son who declared that having received instructions from the Prophet Mohammed he was the Mahdi, or guided one.
He rapidly became the undisputed leader of, depending how you look at it, a religious revival intended to purify Islam or an anti-colonial struggle to expel foreign rulers.
Famously, it all culminated when thousands of the Mahdi's followers - the Mahdi army, to coin an Iraqi phrase - surged up to the governor's palace in central Khartoum and beheaded the senior British officer there, General Gordon.
Winston Churchill was critical of the effects Islam had on its believers
It was a humiliating British defeat and the London press was quick to depict Gordon as a Christian knight martyred by Muslim savages.
Gordon's death was eventually avenged when General Kitchener arrived in Khartoum with some gunboats and an overwhelming force and crushed the Mahdi's followers.
There is a vivid account of that campaign because a young man who was there wrote a book about it all, it is called The River War and the author was Winston Churchill.
Churchill had some fairly strong views on Islam.
"No stronger retrograde force exists in the world. Far from being moribund, Mohammedanism is a militant and proselytizing faith. And were it not that Christianity is sheltered in the strong arms of science, the civilisation of modern Europe might fall."
That was Churchill. This is George Bush: "There are extreme elements that use religion to achieve objectives. And they want us to leave. And they want to topple government. They want to extend an ideological caliphate that has no concept of liberty inherent in their beliefs."
Try this. Next time you see an article about the war on terror in the Western press replace the words "Muslim radical" or "Muslim extremist" with "Mohammedan fanatic" or "savage dervish" and you rather rapidly find yourself back in the 19th Century.
President Bashir said Sudan would not "kneel" to colonialists
My short stay in Khartoum working on the history programme was soon derailed.
Sudan became the world lead story when the International Criminal Court issued the country's president with an arrest warrant for war crimes.
His response was defiant - "a new colonialism," he called it - and, in the streets, as enraged crowds gathered at the site where Gordon had been beheaded, old sensitivities rose to the surface.
Once again, they complained, the West was seeing the Sudanese people as uncivilised savages. The Mahdi took on Gordon. President Bashir is taking on the ICC.
I wonder what General Gordon or Churchill would have thought if, 130 years ago, they had seen that Sufi sect singing and dancing.
Well, we have a pretty good idea about that. One of the phrases Churchill used was "a degraded sensualism, depriving life of its grace and refinement."
And in his diaries Gordon, a very devout Christian, had no doubt that the Mahdi and his men were overexcited natives hell-bent on destroying the civilised world.
Today the language has changed but, for many, on both sides - the basic ideas are much the same.
From Our Own Correspondent was broadcast on Saturday, 7 March, 2009 at 1130 GMT on BBC Radio 4. Please check the programme schedules for World Service transmission times.