When I visited the Berbera prison recently, the warden told me the militants wouldn't see visitors. The guards didn't want trouble. "These men are serving life sentences and have nothing to lose," said one. "They don't give a damn." Finally the warden agreed to let a Somali colleague and me walk past the barred cell, which housed all 11 of the men. It was part of a decrepit free-standing building that stood in the center of a dirt compound.

After seeing the Somaliland port of Berbera, Churchill wrote a tough-minded report. "The policy of making small forts, in the heart of wild countries…is nearly always to be condemned," he wrote. Britain should withdraw from the interior and defend only the port of Berbera. After much debate, London ordered a policy of "coastal concentration." Officers in Somaliland could further arm the "friendlies," but were not to engage the mullah themselves. Chaos ensued, as clans battled each other for ascendancy and loot. Tens of thousands of Somalis were killed.

This was the dilemma that Corfield faced in 1913. The son of a church rector, he had a moralistic streak. But he'd also served in the Boer War and was "made of stuff that does not thrive in offices," wrote biographer H. F. Prevost Battersby. When the Dervishes began marauding against friendly clans, Corfield rashly defied orders and went in pursuit. A Dervish soldier shot him dead 25 minutes after the battle at Dul Madoba began. Some of the mullah's fighters later took Corfield's severed arm as a war trophy to present to their master. "It was a great morale booster for the Dervishes, no doubt about it," says the Somali-born Rutgers historian Said Samatar. "Corfield was a symbol—the British colonial man. In a sense it was a blow against colonialism."

To some in Britain, Corfield was a fool who damaged national prestige by disobeying orders. To others, he was a man of principle—he was "the straightest, whitest, most honorable man I have ever met," said one colleague, displaying the casual racism of the time. The prevailing view was that Corfield's death had occurred, in part, because the British had encouraged the mullah by withdrawing to the coast and seeming reluctant to fight. It "had been proved once more that 'there is nothing so warlike as inactivity,' " wrote Jardine.

We could see figures in the shadows behind the bars. I asked from a distance if anyone spoke Arabic. One bearded man emerged and said with a smile (in Arabic), "Accept God's word, and you'll be safe." Another prisoner, older and larger, told him to shut up, then shouted in our direction: "Get lost, dog," and blew a mouthful of spit. Our guards hurried us away. My Somali interpreter said later that the spitting prisoner was known as Indho Cade, or "White Eyes," and was serving life for shooting an Italian aid worker in the head.

The Islamist radicals see parallels between their struggle and the war waged by the Sayyid. Osama bin Laden's "enemies may call him a terrorist," one top Shabab militant told a NEWSWEEK reporter in 2006, defending the Qaeda leader. It is "something that exists in the world"—a form of infidel propaganda—"to name someone a terrorist, [just] as the British colonialists called the Somali hero Muhammad Abdille Hassan the Mad Mullah."

The militants have sometimes used the mullah's words as a rallying cry. During the American intervention in Mogadishu in the early 1990s, pamphlets appeared in the city with a copy of the Sayyid's poem to Richard Corfield. "Say: 'My eyes stiffened as I watched with horror;/The mercy I implored was not granted.' " It's impossible to gauge the impact the poem had on the thinking of Somali fighters. What is known is that sometime later, militants dragged the nearly naked bodies of American soldiers through the streets, images that were captured on camera and beamed back to the United States.

The decisive turn in the conflict came only years later. In 1920 a decision was taken to send warplanes—one of the early uses of air power to put down an insurgency. Churchill, by now the minister of war and air, had become convinced that air power could do what ground forces had never been able to accomplish. He was instrumental in getting backing for the mission.

The Z Unit arrived in Somaliland disguised as geologists, and assembled the de Havilland 9A planes on site. By this time, the mullah had grown tired of running around the bush and had built many stone forts. On Jan. 21, 1920, he awoke at his fort in Medishe expecting nothing out of the ordinary. He was sitting on a balcony with his uncle, other Somalis, and a Turkish adviser.

According to Jardine's account, Somali aides suggested the spectral objects coming out of the sky might be the chariots of God coming to escort the Sayyid to heaven. But five minutes after a first pass, the pilots returned and dropped bombs. "This first raid almost finished the war, as it was afterwards learned that a bomb dropped on Medishe Fort killed one of the mullah's amirs on whom he was leaning at the time, and the mullah's own clothing was singed," wrote Flight Lt. F. A. Skoulding, who took part in the raid.

For two weeks the planes provided air support to ground forces—including some organized by the mullah's Somali nemesis, Musa Farah. But the mullah, hiding in caves and outwitting his pursuers, again managed to escape. The British made a peace offering; the mullah responded by listing conditions of his own, including a payment of gold coins, diamonds, cash, pearls, feathers of 900 ostriches, two pieces of ivory, and books, all of which he said had been taken from him. Somali allies of the British chased him farther into the bush, where he aimed to rebuild his forces once more. But the mullah succumbed to flu later that year. With his death, his Dervish movement died out.

Many Somalis, not surprisingly, are ambivalent about the mullah. Rashid Abdi, who follows current wars and abuses in the region for the International Crisis Group, recalls learning the Sayyid's poetry as a child, and can still recite some of his verses by heart. He's also aware that the mullah was a warlord who committed abuses very similar to those that Abdi chronicles today. "There is nobody who can claim to be a Somali historian who can whitewash the atrocities of Muhammad Abdille Hassan," Abdi told me on a phone call from Nairobi, Kenya, where he's stationed. "He wanted to unify the Somalis, and if he had to break a few clans to do that, he would. In the evening he might craft a poem about his dying horse, and the same day he might have burned down whole villages, killing hundreds of people. It's the nature and the tragedy of how Somalis have existed all through the years and centuries."

Hadraawi, a renowned Somali poet who goes by a single name, has mixed feelings about the Sayyid. "He was a power maniac…a dictator," he says. Still, Hadraawi admires the man for his unequaled talent as a Somali poet and the leadership he showed in the struggle against colonial powers. "He was the light I was following in my youth—my guide," says Hadraawi, who was a teenager during the heady days of Somali in-de-pend-ence in 1960. "It was later on that I realized his mistakes." Hadraawi still rejects the name Mad Mullah—mostly, he suggests, because it's a simplistic caricature.

Hadraawi is my companion on a trek to the Black Hill. The journey from the capital, Hargeisa, is long, but not as difficult as it was in Corfield's time. To get there, a foreigner is required to fill out an "escort-authorization form" for the "Special Protection Unit" of the police and hire two armed guards for $20 a day. The area is much safer than the chaotic mess to the south, or the pirate-infested coastline of Puntland to the east. But ever since terrorists killed the Italian aid worker and two British teachers in 2003, the government has required foreigners to travel with armed guards.