We reached Maiduguri in the dark. A city of about 1.5 million, it’s the capital of Borno State in northeastern Nigeria. Maiduguri felt different from Kano. On edge. Six months earlier, in August 2009, a radical Islamic sect called Boko Haram (“Western education is forbidden”) had started a jihad in Maiduguri, rioting and bombing police stations and government buildings. In response the government destroyed the group’s mosques, and its leader died in police custody while wearing handcuffs. Nearly 1,000 people were killed.

When we arrived, Boko Haram had gone underground, but it still haunted the city, or at least my perceptions of it. (I later read that Eliza Griswold, who wrote The Tenth Parallel (2010) about her travels along that latitude in Africa and Asia, where Islam and Christianity often mix uneasily, called Maiduguri the most alarming place she visited.)

The city seemed poorer than Kano, with more garbage everywhere and even less electricity. After sundown, most of this major city went dark. Smoke from thousands of fires turned the night hazy and stung the eyes. Dense waves of buzzing motorcycles swirled and eddied in the gloom. Their exhaust contributed to the choking murk. Most carried at least one passenger, often a robed woman riding side-saddle, sometimes an entire family, the children somehow tucked between parents. People walking on the side of the road in the pitch dark flashed by in our headlights like briefly illuminated ghosts. The smoke and noise and mobs of motorcycles zooming from the darkness and vanishing back into it made driving at night spooky, almost surreal.

Nasiru Datti, Abdul, Nasiru Wada

So, in a different way, was our hotel, the Maiduguri International. Modern institutional in style, it was succumbing to decay and mold. Only two of its floors remained open. In the long corridors, dim bulbs, widely-spaced, barely dented the dark, whenever the capricious electricity was working. The carpets were sodden. The ambitious swimming pool was now green with scum, and tall weeds grew from cracks in the tennis court.

By contrast, the red-brick palace of Bornu’s shehu, or sheikh, looked crisp and shipshape. Built in the 1940s, it had replaced one built in the early 20^th century when the capital of Bornu moved here from Kukawa. Bornu has always been famous for its horses, and the sheikh had a stable of them.

Next to the palace, a huge mosque was under construction. A long sandy piazza fronted both. At night, by tradition, the piazza became a play-space for children.

One night, watching them play outside the palace, we met a district official dressed in a beautiful robe and cap. “Your sultan should come visit us in Kano,” said Nasiru Wada, “because he is our slave.”

The official stared at him, then roared with laughter. “No!” the man shouted. “You are all my slaves.”

This exchange had a history. Nasiru Wada and Nasiru Datti were Fulanis from Kano who spoke Hausa. In Bornu, the predominant ethnic group were Kanuris, who spoke their own language. Slave jokes, Nasiru Wada told me, were common between the two groups.

The reasons stretched back 200 years. The Islamic kingdom of Bornu rose to power when Europe was in the Middle Ages. Early in the 19^th century, when the Fulani scholar Usman dan Fodio led the jihad that brought much of central Sudan under his control, he was unable to conquer Bornu. His brilliant son, Muhammed Bello, fared no better. Nor had Bornu been able to overthrow dan Fodio. For much of the century, the two kingdoms alternated between tense détente and slave raids into each other’s territory. If either kingdom had managed to defeat the other, the vanquished would have become the conquerors’ slaves. This was the history behind Nasiru’s joke and the official’s retort.

Though Kano and Maiduguri are only 300 miles apart, the Hausa and Kanuri languages are completely different. “They talk and I cannot understand one word,” said Nasiru Datti. Communication between the groups occurs in Hausa, which is more widely spoken. Barth was fluent in both.

He also preferred the dispositions of Hausas and Fulanis to Kanuris, calling the former cheerful and vivacious, the latter dour. Both Nasirus nodded at this. “They aren’t friendly,” said Nasiru Wada. “They are tough people, very tough.”

In the early morning, Maiduguri’s ghosts seemed less apparent. We went to an open-air tea shop. A wood fire heated a huge samovar. The owner mixed black tea with milk and poured the mixture back and forth between cups in long arcs, then served it. His partner cut thick slices of dense white bread and slathered it with butter. Two dozen men and boys chatted and ate breakfast, squatting or sitting on crude benches and wooden stumps.

“I’ll try,” he said, shaking his head, “but Kanuris are very tough. Very tough.” He asked. She studied him coldly, then me, then nodded curtly. She didn’t smile for the camera.

Several months after we left Maiduguri, Boko Haram emerged from underground. Energized and organized, they began targeting government buildings and churches in northeastern Nigeria. Over the last two years Boko Haram seems to have affiliated itself with other radical Islamic groups in north Africa, and may have received training and funding from al-Qaeda. They have claimed responsibility for dozens of bombings and hundreds of deaths, and are intensifying their operations. In January 2012 they began a campaign of terror in Kano, previously untouched by the violence.