Host: Between the 15th and the early 19th century, Africa's kingdoms would witness remarkable changes in the religious, economic, and cultural trajectory of the continent.

By the early 16th century, at least 3 African kingdoms were directly connected to the royal courts of Europe and even to the halls of the Vatican.

Europe's exploration of the Americas would become one of the most defining experiences in the continent's long history.

This New World would become synonymous with trade, and a crucial component of trade would be the shipping across the Atlantic of some 12.5 million Africans.

Powerful empires would rise and fall, all across the continent, during this time of seismic global change.

In the far north corner of Angola, on a flat-topped mountain, lies the city of Mbanza Kongo, the capital of Zaire Province.

Today, it's home to 100,000 people.

6 centuries ago, this city was the capital of one of Africa's greatest kingdoms.

At the end of the 15th century, the Kingdom of Kongo was one of the largest and most powerful states in the southern half of Africa.

From the capital, Mbanza Kongo, a densely settled and well-administered city lying south of the Congo river, a king presided over a highly stratified society that covered some 50,000 square miles.

At the heart of the city stand the ruins of a building constructed in the middle of the 16th century.

It's one of the most important architectural remains in the history of Sub-Saharan African Christianity-- a striking symbol of the transformation of the religious beliefs of this great African kingdom.

It's the cathedral of Sao Salvador.

What did you think when you first heard there was an African cathedral before the 1600s?

I couldn't believe it.

Tell me about it.

The cathedral was built in 1549.

Mm-hmm.

And it's an incredible thing.

Think about having a cathedral to fulfill the destiny of Christianity in Africa.

Do the people here know about this history?

Many of the reference say the place was a temple that connect to the old religions.

So that would make sense.

That makes sense.

Uh-huh.

The second tale is always the king knew he wanted to be a Christian and he decided to build this monument, to honor this incredible transformation.

Host: The adoption of Roman Catholicism by the king of Kongo in 1491 not only changed the official religion of the kingdom, but it inserted Kongo into the very heart of European power.

At the beginning of the 17th century, a summary of world rulers prepared in Florence for the education of Prince Cosimo de Medici listed the leaders of the world's great kingdoms.

Alongside the monarchs of such great powers as England, France, Japan, and China, was King Alvaro II, the king of Kongo.

The ruler of a powerful African kingdom converts to Roman Catholicism in 1491, sends his own ambassadors to the royal court of Portugal and to the Vatican, and one of his successors, in Shakespeare's time, is listed as one of the world's great rulers?

How could every school child not be taught this about the history of the great African continent?

The Atlantic coast of Africa.

Long a barrier to contact and trade, these waters were about to be transformed into a gateway.

Early in the 15th century, Portuguese navigators discovered how to use the winds and currents of the Atlantic not only to sail south, but, for the first time, to return home, north, to Europe.

This remarkable navigational breakthrough opened heretofore unknown lands to the south, heralding the European age of discovery, vastly expanding Europe's understanding of the known world.

In 1483, a ship dropped anchor at the mouth of the Congo River in what is today the country of Angola.

Its captain was the explorer Diogo Cao, dispatched on a mission by King Joao of Portugal to seek out new lands, luxury goods, and powerful allies.

When Cao reached the shore, he marked one of the most important encounters in world history by erecting a limestone pillar.

How do you feel when you see this?

Woman: It's a major event in global history.

Cao was very fortunate that he met a very friendly welcome upon his arrival and the king of Kongo and his court were filled with optimism about the relationship where both parties would benefit from exchanges that would be made.

So let's make a deal.

Yes.

Host: The Portuguese arrived with gifts of silk, satin, and velvet.

They were seeking trading relationships with African kingdoms that they assumed were rich in silver and gold.

What did the king and his nobles make of these visitors, and what would this new friendship mean for the Kingdom of Kongo?

Over 100 miles inland, at his capital of Mbanza Kongo, Nzinga Nkuwu, the Mwene Kongo, or ruler, graciously received the Portuguese visitors, keen to create cultural and religious links with his kingdom.

Man: Essentially when the Portuguese came to west Central Africa, it was almost like two continents that didn't know about each other's existence suddenly reaching and meeting each other.

Woman: It in fact allowed the king of Kongo to connect with an outside power.

It wasn't a local power, it was an outside power which, in fact, meant that Kongo became part of what was emerging, which was the Atlantic world.

Host: In addition to engaging in cultural interchanges, the Kingdom of Kongo could now trade directly with Europe for the first time, exchanging copper and ivory as well as luxurious raffia cloth, which soon became highly prized throughout the courts of Europe.

But for Kongo, the relationship wasn't exclusively commercial.

It allowed them to play in the European political game in a way that, um, other countries really didn't have access to.

It's not that they could force anybody in Europe to do anything they wanted, but they could-- They, first of all, knew the political geography of Europe much better than other African rulers did.

At the end of the 15th century, we know that the Portuguese and Kongo had a significant relationship.

By 1488, Kongo and Portuguese had exchanged ambassadors.

The Portuguese were interested in having the Kongolese give up their idols and other fetishes, as they said, and, you know, become Christian.

So in 1491, the king of Kongo, Nzinga Nkuwu, converted to the Catholic faith.

Host: Through this conversion, the Kingdom of Kongo entered an even bigger world in its alliance with a growing European power.

Heywood: The Portuguese wanted to expand, to have prestige.

It had been close to the Vatican and had been given the world of the Atlantic to expand.

God, gold, and glory, the 3 Gs that propelled the Portuguese to go into the Atlantic.

But the religious dimension was also important, because one of the main aims was, in fact, to spread the Catholic faith.

Host: Kongo's commitment to their new religion would deepen further when Nzinga Nkuwu was succeeded by his son Afonso.

Afonso wrote that he fought and won a battle of succession over anti-Christian forces to take the throne at the beginning of the 16th century.

Heywood: He was very devout, and he really was very much, um, transformed and intrigued.

He studied a lot.

Host: A Portuguese missionary noted Afonso's extraordinary faith and piety: "It seems to me from the way he speaks he is not a man, "but an angel, sent by the Lord in this kingdom to convert it.

For I assure you, it is he who instructs us."

It was Afonso who developed the school system, for example, put masters, school masters, in every province and arranged for an educational system, sent many, many people to Europe to study.

He addressed the king in Portugal as his brother.

He really wanted to have an equal type of relationship where he would be seen in Africa as a powerful Christian country.

Host: Christianity was at the heart of Afonso's kingship, and so was its control.

He made certain that the faith was taught primarily by his own teachers, rather than by European missionaries.

He self-consciously ensured that Christianity practiced in his kingdom had a distinctly indigenous character.

A mix of Roman Catholic beliefs constructed on a foundation of African spirituality.

Kongo's craftsmen transformed the iconography of Roman Catholicism, making it their own.

LaGamma: This was created by a local brass caster, Kongo artist who is interpreting Christ in a Kongolese idiom.

Yeah, a Black Christ, an African Christ.

Initially, European prototypes are used at the court, and eventually, local brass casters are reimagining the forms in their own local aesthetic.

That's one of the most powerful crucified Jesuses that I've ever seen.

It's so deeply moving.

And the way that the textile is emphasized, it reminds us of the textiles that were so important as part of the artistic production of this great civilization.

So even the loincloth that protects Jesus is Kongolese.

Not only is Catholicism Kongolese, but Jesus is Kongolese as well.

Afonso was devout, and wanted his kingdom to be formally recognized within the Catholic Church's hierarchy with its own bishop.

Afonso's son Henrique, educated in Portugal, was appointed bishop by Giovanni de Medici, Pope Leo X, in the year 1518.

The Kingdom of Kongo joined Nubia as the home of an African bishop.

It's not that he wanted primarily his son to go to heaven as a bishop.

He wanted-- It was a power move.

Yeah.

It's a power and political move, to allow someone to have power within the system.

Host: To mark the appointment of his son as bishop, Afonso sent the pope an extraordinary work of art.

Not only is it beautiful, it's meaningful.

LaGamma: This is one of the treasures of world art.

It's one of the earliest works by an African artist to wind up in a great European art collection.

And it is appreciated as something of exquisite elegance, beauty, and preciousness.

Host: While this vibrant religious and political alliance between Kongo, Portugal, and the Vatican was deepening, a prosperous economic alliance was also flourishing, and one commodity in particular would become a key economic driver in an emerging Atlantic global economy: sugar.

In the early years of the European Renaissance, cane sugar sold, pound for pound, for as much as the most exotic spices imported from Asia.

Cultivation first on Madeira, then on Sao Tomé and Príncipe, would make Portugal one of the world's largest sugar producers by the middle of the 16th century.

They already knew that any tropical islands was likely to be a place where you could grow sugar cane.

And so they immediately worked on making sugar cane a production of that island.

Already by 1500, they are growing sugar cane on Sao Tomé, and they're sending it back to Europe.

Host: Sugar had been cultivated by Europeans for hundreds of years, in the Levant, on Cyprus and Sicily, in Spain, and now in the mid-15th century, off the west coast of Africa.

There was just one problem: harvesting and processing cane sugar was backbreaking work.

To solve this, planters turned initially to European indentured servants, but ultimately the dominant labor force in sugar cultivation would be Black African slaves, and a long succession of African kingdoms-- including King Afonso's Kongo-- would be willing partners in this lucrative trade.

Thornton: Kongo wanted to import goods from Europe and in order to do that, they had to have goods to export.

Kongo exported ivory, copper, um, rare animals during the course of its commercial relations with everybody that visited their shores, but by value, by far the largest contribution that Kongo gave was in slaves.

Host: Slavery is as old as civilization itself.

It played a key role in African kingdoms and was certainly an important component of the domestic economy of the Kingdom of Kongo.

The enslavement of other people-- enemies, captives in war-- was a crucial factor in the expansion of the wealth of the Kongo kingdom, and the Portuguese could readily purchase these slaves in Kongo's already-existing markets.

Thornton: Kongo was still an expanding country, it was conquering neighboring areas, and part of that expansion involved the enslavement of people and their transport back to Kongo.

Host: Afonso was happy to sell slaves to Portugal.

It made great business sense.

But he had very strict rules about who exactly could be enslaved and sold.

Thornton: There was this very strong idea that the kings of Kongo could decide who was a slave and who wasn't.

There were procedures for who could be enslaved and generally speaking, it was outsiders or foreigners that could be enslaved.

Kongolese really couldn't be.

So this was a very protective relationship they had with their own people.

Host: But Portugal was ignoring the rules of who could and could not be enslaved.

Afonso was in danger of being undermined.

In a letter that he wrote to the king of Portugal, he complained bitterly.

Each day the traders are kidnapping our people, children of this country, sons of our nobles and vassals, even people of our own family.

This corruption and depravity are so widespread that our land, he wrote, is entirely depopulated.

Heywood: If you were going to involve yourself in international trade, you had to pay with slaves.

So the choice that the Kongolese had was to either withdraw from the trade or continue the relations and try to control it.

Host: But fundamental shifts in global history would gradually change the nature of the relationship between Africa and the rest of the world.

The trading relationship that developed between Kongo and Portugal was fundamentally shaped by a discovery thousands of miles away on the other side of the world.

A year after the king of Kongo converted to Roman Catholicism in 1491, Christopher Columbus set foot on an island he named Hispaniola.

The discovery of these new lands across the ocean had a seismic impact on world affairs and ignited a race for riches that would turn the world upside down.

The mastery of the winds and currents that had brought the Portuguese south, to the West African Coast, also took Spanish and Portuguese ships west, to a new world on the other side of the Atlantic.

In 1500, the Portuguese landed in what's today Brazil.

Portugal was expanding and its empire was growing.

The world was experiencing epochal change.

A triangular Atlantic economy would link Europe and its African trading partners with the new lands in the Americas, which offered enormous opportunities for mining silver and gold, for growing sugar and tobacco, and manufacturing rum.

Demand for these products would be seemingly insatiable, fueling the desire to maximize profits through a large, cheap labor force.

The demand for labor, large numbers of people to work in the plantations and the mines of the New World producing sugar, producing tobacco, producing, ah, cotton.

The large demand for labor was not fulfilled through the use of the indigenous people.

Host: Kongo's admiration for Portuguese culture was expressed in their embrace of Christianity and desire to be part of the community of Christian nations.

Ironically, the principal commodity that Kongo possessed to pay for its social engineering was slaves.

In 1575, the Portuguese did something that no other European colonial power had thought to do.

They made a deal with the king of Kongo to create their own city, which became the city of Luanda.

Why was this important?

Because they could use this as a base to capture Africans whom they used as slaves themselves in Luanda, but also to capture Africans whom they sold across the ocean in the transatlantic slave trade.

It was a brilliant commercial move.

More and more slaves were channeled through the port of Luanda, eventually leading to an astonishing total number of 1.4 million.

They were hooked on a commodity and if it meant having a few more wars to get a few more captives to sell to the Portuguese, which turned out to be a lot more rewards and a lot more captives, then that was fine.

It was a trade that, for the African kingdoms, had tremendous importance because of the ambition of the African kings to participate in the commercial and diplomatic and political network of the Atlantic world and the main currency that they had at their disposal was the enslaved labor.

Host: The Portuguese came to Luanda with the blessing of the king of Kongo, entering into an alliance with the Kingdom of Ndongo.

That alliance didn't last, and in 1579, the king of Ndongo attacked the Portuguese, setting off a conflict that would last nearly a century.

Those wars eventually produced a vast quantity of slaves.

And it was this huge wave of slaves that became available through Portuguese, um, basically Portuguese conquests, Portuguese direct military efforts in this area that fired up the Brazilian sugar industry.

Host: Ndongo had fought Portugal to a standstill by 1600, but the Portuguese brought up bands of fighters from the south, the Imbangala, the ferocious warriors and mercenaries purported by the Portuguese to be cannibals.

They helped the Portuguese to win many battles against Ndongo.

Out of this chaos would emerge one of the most charismatic and enduring characters in all of African history.

A fearless warrior queen and formidable politician who remains an icon in Angola today.

In her lifetime she ruled over two powerful kingdoms-- Ndongo and Matamba.

Her name was Njinga.

In 1622, after several years of fierce fighting with the Portuguese, Njinga was dispatched by her brother, the king Ngola Mbandi, to negotiate a peace settlement with the Portuguese governor, but not to surrender.

When Njinga arrived at the meeting, she wasn't accorded the treatment she expected as a representative of an independent kingdom.

What Njinga did next has become the stuff of legend.

A symbol of African pride and resistance in the face of attempts at European domination.

She arrives for her audience with the governor and he's sitting in the Portuguese style of velvet chair, and she enters the room and sees that they had prepared cushions and carpet for her to sit on the ground.

And at that point she looks over at one of her attendants, who goes and crouches on the floor and Njinga sits on her, the same height as the governor.

So she confronted the governor eye to eye.

Exactly, eye to eye.

Host: By the end of her trip to Luanda, Njinga had won significant concessions from the Portuguese.

In return, she agreed to convert to Christianity.

She had proven to be a supremely able negotiator.

She said, "How can you demand tribute of someone who is free?

You know, my state is free."

And she was very persuasive.

And she was able to get the governor and the Portuguese to agree to the terms that they will remove the troops from Ndongo.

Host: Two years later, in 1624, Njinga's brother, the king-- unable to defeat the Portuguese-- by some accounts was poisoned.

By other accounts, he committed suicide.

When the throne suddenly became vacant, Njinga became one of the contested successors.

And with the support of the army and a few other key allies, not surprisingly, she emerged victorious.

Although the Portuguese were impressed with Njinga as an ambassador, they didn't want her to be the monarch.

Heywood: The Portuguese did not want Njinga to be queen because they knew that she was going to insist on Ndongo being independent.

Their argument was that Njinga being a female was not eligible to rule.

Host: The Portuguese backed some of Njinga's subordinates, and she was ousted in a war waged against her in 1626.

But Njinga refused to fade away.

From 1626 to 1657, she kept fighting the Portuguese.

Host: Now deposed, Njinga conquered the independent kingdom of Matamba.

As ruler of Matamba, she began to assemble an army and, pragmatically, joined forces with her former enemy, the martial and reputedly cannibalistic Imbangala.

Heywood: She had to be strategically very astute.

Even though she became an Imbangala, she insisted that she never actually consumed human flesh or had joined in many of the rituals.

Host: When the King of Kongo, Garcia II, invited the Dutch to invade Angola, Njinga immediately contacted the Dutch to join them.

Both Garcia and Njinga wanted the Portuguese out of Angola, and saw the benefits of an alliance with the Dutch.

So it's a time when the Dutch are in Brazil and are trying to establish a colony of their own there, and again, there is no Brazil without Angola, so they need to seize Luanda as the source of enslaved labor, and Njinga as well as the king of Kongo really took the opportunity to plot and ally themselves with the Dutch against the Portuguese in the, you know, the enemies of my enemies are my friend.

Host: The Portuguese were pushed out of Luanda by the Dutch in Kongo.

The Dutch captured the city, but the Portuguese retreated to inland forts and kept the war going.

The struggle was now mostly between Njinga and the Portuguese.

One of the misconceptions about Njinga is that she was anti-colonial, meaning she didn't want Europeans to be on the African continent, but isn't it true that she just didn't want them trying to capture her kingdom?

She was not pushing away European colonialism, she was just trying to control her territory and control the means by which she could remain queen.

Host: In 1657, Njinga and the Portuguese negotiated a truce.

After 30 years of war, she had won back part of her original kingdom.

Now she was queen of Ndongo and queen of Matamba.

6 years later, at the age of 81, Njinga--still a devout Christian--died.

I think she died having really changed the region and her claims to the throne really created a new creation myth for the kingdom Ndongo and Matamba, and one testament of it is after her for about the 100th year after her death, the Kingdom of Matamba was ruled by women.

Host: The combination of avarice, aggression, and warfare would make Angola the single largest source of slaves, by far, in the history of the transatlantic slave trade.

Far more slaves were shipped to the New World from west Central Africa than from any other part of the continent.

That's 5.7 million people over roughly 350 years.

Most of those went to South America.

But about 24% of the ancestors of the African American people came from this region, too.

Incredibly, 2.8 million Africans were shipped from Luanda alone.

If we add another 800,000 from the nearby city of Benguela, that means a quarter of all slaves who crossed the Atlantic Ocean started their journey from what is today the country of Angola.

All along Africa's west and central Atlantic coast, Europeans marked their presence with coastal forts.

These forts now became commercial hubs where much of this enormous and growing business between Europeans and Africans was conducted.

With the Portuguese and the Spanish, the Dutch, the British, and the French now boasting colonies of their own in the Americas, the demand for slaves grew greater than ever.

In the 18th century, the transatlantic slave trade reached fever pitch.

Just over 50% of all transactions occurred over the course of this century alone.

On average, an enormous 65,000 Africans a year were being exported from these shores, reaching a staggering peak of 108,000 in the year 1791.

The port of Ouidah, in what is today the country of Benin, was the busiest slave market in West Africa.

An estimated half-million slaves were traded from here across the Atlantic during the 18th century.

That port belonged to a small but strong kingdom that had emerged as one of the most powerful states along the region nicknamed "The Slave Coast."

It was called Dahomey.

Man: Dahomey emerges in the early 17th century.

According to historians who have worked on Dahomey, it functioned in its early years as a mercenary group and it hired itself out to neighboring polities who had disputes.

The accepted interpretation was that, ah, these inhabitants of the Abomey plateau saw the flourishing of Atlantic trade and wanted to be part of it.

Host: And in order to be part of this booming trade, this inland kingdom had to expand.

In the 1720s, led by its fifth king, Agaja, Dahomey fought to gain control of the vital ports of the kingdoms of Ouidah and Allada.

Thornton: He needed to have a coastal position.

The occupation of Ouidah and Allada would give him that.

Um, and so in that first period you can imagine that the sort of the flood of slaves is as a result of these expansionist wars.

Host: It's difficult to imagine a kingdom more militaristic than Dahomey.

Each king was given a mandate to expand the reach of the kingdom.

And that meant going to war.

Thornton: And Agaja writes a letter to the king of England, and in this letter, he's boastful.

Among the things he says is, he talks about, he's a great conqueror and he's taken over 209 kingdoms, and his father did fewer than him and his grandfather did even fewer than that.

He also says, you know, I've completely left off the use of local, uh, weapons, and I'm now a great lover of firearms.

Host: Throughout the 18th century, Dahomey's expansion put it into conflict with rival kingdoms.

After the conquest of Ouidah and Allada, her enemies were Porto-Novo to the east, Great-Popo to the west, and Oyo to the north.

Dahomey waged wars.

When they won the wars, there was a slave trade, when they lost the wars, there was a slave trade because somebody bought those slaves that were, Dahomeans that failed to win, because, uh, their--the opponents' armies that they were waging war against were prepared to sell slaves as well.

Host: Many European accounts after the 1850s focused on Dahomey as militaristic and violent, most notably for its practice of human sacrifice at a festival called "The Annual Customs."

But even as Dahomey engaged in wars with its neighbors, it also had a vibrant artistic culture.

The culture encompassed a dynamic religion called Vodun, which was transported across the Atlantic by enslaved Africans and transformed into Vodou, long maligned in the West.

The kingdom also had a unique and distinctive canon of art and architecture.

At the heart of this city was a vast complex of royal palaces.

Woman: Every palace is a special, uh, construction.

You have, uh, it's a big palace for one king, and then you have all those palaces, ah, 12 palaces, ah, next to one another.

Very good for the architects in the kingdom, and the builders?

Yes, of course.

But the architects, the artists are a very important part of Dahomey of 18th century.

Host: Those artists were responsible for the elaborate bas-reliefs that adorn almost every wall of these palaces.

They're a record of Dahomey's history, culture, and religious beliefs.

Traditionally, artists fashioned these reliefs from earth taken from termite mounds, which had been waterproofed by the insects' saliva.

Each relief expresses its own individual narrative and symbolism: monarchs are depicted allegorically as powerful animals.

The king's throne was built on a foundation of severed heads of vanquished foes.

This royal art was intended to underpin and reinforce the power of the state and that of its rulers.

The king used women as soldiers to expand royal power, and struggles waged with non-royal nobles, who controlled sections of the army and administration.

Akyeampong: The use of women was extraordinary.

Kings of Dahomey would deliberately choose wives from areas that had recently been incorporated.

So that by courtesy of choosing a wife from that area, that area felt vested in the state or in the Kingdom of Dahomey.

Dahomey also practiced this thing where every political position outside of the palace was mirrored by a woman inside the palace.

She mediated your access to the king.

And it's called doubling, so every position was doubled by a woman and it was a way in which the king kept political officers at bay and their ambitions in check.

Host: The back and forth struggle between 4 kingdoms over control of the coast created tremendous regional instability, and many people were taken as slaves.

Amassing the means to fight these wars was heavily dependent upon the sale of slaves; and the sale of slaves could make African rulers extremely wealthy.

Heywood: There was a lot of ways in which the African elites are in many ways responsible for, in fact, exploiting their own people and transforming systems of dependency in Africa to tie in with the demands of the slave trade.

Host: Millions of human beings were traded for a fraction of what they might have produced in their lifetime at home.

Some of the fittest and ablest of the African people were working thousands of miles away creating the wealth of plantation owners in the New World.

The slave trade robbed the continent of its most valuable resource-- its people.

Abaka: The skills of these Africans were highly valued in the New World.

I mean, in the Carolinas, for example, it was a skill of rice cultivation.

Um, in other parts of the New World it was the skill of making implements, of making weapons, um, the skill of being able to use herbs, for example, to heal people.

Heywood: Those Africans brought with them, you know, religious values, they brought with them notions of community, notions of kinship.

So enslaved Africans maintained their humanity even despite the fact that they became units of commodity in the trade.

And that's what you have to look at, that human beings survive.

Host: The slave trade's impact affected both the size and structure of the African population, because many buyers initially sought adult males for the arduous labor in the new world.

Whether it's male or female, it has an economic impact.

If you're left with your youngest and your eldest members of society, you're left with a huge gap.

Host: The capture and deportation of so many more adult males than females left an imbalance that sometimes reached two to one, a phenomenon acutely and painfully captured in this 19th-century work from the Yombo people located in today's republic of Congo.

What does this sculpture tell us about the position of women in Kongolese society at this point in its evolution?

LaGamma: By the 19th century, women are having to shoulder increased responsibilities in Kongo society.

The young male labor force has been radically diminished.

Because of slavery.

The slave trade.

The Atlantic slave trade.

It's about the heightened importance that women are taking on as caretakers of society.

Host: Resistance to the slave trade ran from the state to the individual.

Some states, such as Benin, only participated sporadically.

Most people were enslaved during warfare, others by bandits or by judicial order.

People often fled to safe places either fortified or protected by difficult terrain.

Abaka: In northern Ghana, for example, among the Kassena people, people adopted very serious and very effective forms of resistance.

People took to the hills.

They carved out spaces in the hills where they could go and hide from the depredations of the slave raiders.

Host: This is Ganvie on Lake Nokoue in modern-day Benin.

The Tofinu people who lived here, fishermen for the king of Porto-Novo, used the swampy land around the shores of their lagoons as a natural fortress, an ideal protection against attacks.

Thornton: The coast in that particular part of Africa is characterized by having a lagoon system that runs parallel to the coast, so you have, uh, swampy lands and islands and so on.

Host: Ganvie's diverse population included Tofinu slaves but also refugees fleeing the wars waged between Dahomey and Porto-Novo for control of the lagoon region after the fall of Allada in 1724.

Even when people from rival kingdoms settled here, they found ways to work together to defend themselves from capture.

Abaka: Using the topography, they were able to resist enslavement in West Africa-- secret societies.

In some places, children, women's organizations, these were all turned into what we can call today early warning systems.

They had a system of notifying people, of sounding the alarm whenever they were under attack.

Host: A fight against injustice and exploitation would trigger enormous social change throughout West Africa.

A holy war would give rise to what would become one of the largest and most culturally vibrant empires in African history: the Sokoto Caliphate.

As the 18th century drew to a close, far inland a revolution was stirring.

The driving force behind it would be powerful new ideas.

It was sparked by the dream of a young Muslim cleric called Usman dan Fodio.

Dan Fodio was a teacher in one of the royal households in what is today modern Nigeria.

This royal household was one of 7 kingdoms that together formed Hausaland.

In the last decade of the 18th century, one of these kingdoms, Gobir, found itself vulnerable to attack from within, in response to the religious practices of the royal family.

Man: Usman dan Fodio was close to the centers of royal power, but there were things about the exercise of power that he found really problematic.

And I think that there was a certain amount of, of, uh, alcohol consumption and womanizing that, that, that any kings, uh, you know, frankly, uh, tend, tend towards.

[Man chanting prayer] Ware: But one of the major issues in his time is that increasingly, Muslims are being traded as slaves.

And Islamic law forbids, specifically, Muslims enslaving other Muslims.

Um, and this had become a major problem since the time of the rise of the Atlantic slave trade.

Host: Fired by religious zeal, dan Fodio began denouncing the rulers of Gobir.

Ware: What happens is he begins preaching, and he begins preaching against all kinds of injustice in the society, especially this problem of Muslims enslaving other Muslims.

And all of the people who have been victimized by this increasingly predatory regime of the Hausa states start to gather around Usman dan Fodio.

Which then makes the rulers worry about him that much more.

Host: Dan Fodio's preaching eventually brought him into conflict with one of his former pupils, the king of Gobir, who objected to dan Fodio encouraging his followers to arm themselves.

In 1801, dan Fodio was exiled to the rural village of Degel where his preaching would soon turn into armed conflict.

Ware: The last straw is that there's a skirmish between the rulers of Gobir and, uh, dan Fodio's men.

And 300 of his soldiers were taken captive.

Now, these weren't just ordinary soldiers, these were literate scholars, thought of as the exemplars of piety.

And instead of being ransomed, they were sold as slaves.

And that's when Usman dan Fodio says, that's it, we ain't got nothing to talk about no more, we got to fight.

Host: One night, a great Sufi mystic appeared in dan Fodio's dreams, and this is how he described the encounter.

"He addressed me as imam of the saints "and commanded me to do what is approved "and forbade me to do what is disapproved.

"And he girded me with the Sword of Truth to unshackle it against the enemies of God."

He was given explicit permission to fight.

And he...wasn't going to take that action until he felt he had some kind of divine permission to do so.

Host: Between 1801 and 1808, dan Fodio and his soldiers would conquer all the Hausa city-states, and from this they would create a new state.

Dan Fodio, now titled Amir al-Mu'minin, the commander of the faithful, executed the king of Gobir and established a new center of power at Sokoto.

The Sokoto Caliphate had been born.

The Hausa country had never been united under a single political ruler and all of a sudden, not just the whole of the Hausa country but a good chunk of neighboring areas were also brought into the Sokoto Caliphate, which was one of the largest in terms of population and surface area, um, political unit, ever created in Africa.

Ware: Complete and total revolution.

Up becomes down, down becomes up.

And one of the main reasons why the revolution is effective so quickly is that Usman dan Fodio offers freedom to the slaves of his enemies.

Host: Dan Fodio had drawn on a longer West African tradition of revolution, questioning state oppression, the slave trade, and injustice, such as the jihadi revolution in Futa Toro, led by his contemporary, Abd al-Qadir, which started in 1776, the same year as the American Declaration of Independence.

At its height, the Sokoto Caliphate was one of the most powerful empires in Africa.

Its government, based on strict Islamic principles of morality and justice, would shape the politics of the entire region right to this day.

Sokoto was a new kind of state: in the past, scholars had served as counselors to kings.

But now the scholars themselves were running things.

Ware: One of the major outcomes is that African languages now become languages for scholarly production.

That opens the world of Islamic thought and Islamic scholarship to new constituents.

Host: Here in Sokoto today, these handwritten manuscripts are still cherished as a direct link to the spiritual message of the caliphate and the teachings of Usman dan Fodio himself.

So ordinary people benefited from that kind of scholarship, because the scholarship was not confined in the use of Arabic language only.

In fact, they translated most of their works into the local languages.

Fulfulde, Hausa, which are the two pro-- predominant languages in this part of Africa.

So everybody benefited.

In fact, even today, you hear some of their works being sung in mosques and the public gatherings.

So as a result, many people got their education through that kind of system.

Host: Dan Fodio's revolution was social as well as political-- not just a jihad of the sword, but also of the heart.

Woman: When Sheikh Usman dan Fodio started his jihad, he met women in abject poverty, with illiteracy.

He believed that women should be well taught and should be emancipated.

So he started teaching his children, his family members, and people in the community.

Host: One of the most revered people to emerge from dan Fodio's revolution was not a warrior but a poet.

She was Usman dan Fodio's daughter.

Her name was Nana Asma'u.

Her life and works are still celebrated today.

Omar: Asma'u was a very brilliant person, so she, her father taught her and other members of her family were very erudite scholars, they taught her.

She learned the Quran, she learned Islamic jurisprudence, she learned the prophetic tradition.

She also learned areas of mathematics, languages, politics, and what have you.

And by the time she was married at the age of 14, she was also married to a learned scholar, Gidado dan Laima, who continued to teach her, and by the time she was less than 20 years, she had started teaching children and women.

Host: The scale of the Sokoto empire gave it a huge trading advantage.

The size of its internal market alone boosted textile production and contributed to a dramatic increase in the kola nut trade, one of the stimulants allowed by Islam.

Every aspect of trade was booming, including the trade in people.

Only non-Muslims could be enslaved, and slaves could convert to Islam and then be freed.

But still, some two million human beings were kept by the Sokoto Caliphate as slaves, mostly working in the fields.

In fact, Sokoto had the most slaves of any state in the whole of Africa.

[Men calling prayer] Ware: This is one of the great ironies of history, is that a war that begins, in part, to prevent the enslavement of Muslims ends up leading to probably more enslavement than what had come prior to it.

And even Usman dan Fodio himself warned against the way that he saw his revolution turning, when he was too old to be able to do anything about it.

He said that when we enter a town and we enslave free people, know that the fire will enslave us.

Host: Dan Fodio's holy war of the late 18th century established a caliphate that still exists to this day.

It would also inspire holy wars elsewhere in West Africa.

In the wake of Sokoto, there would be the rise of Islamic empires of Massina and Toucouleur.

This was a time of revolution globally.

The American Revolution, the French Revolution, and the Haitian Revolution-- all reactions against tyranny and inequality, leading to new definitions of justice, and Africa would be no different.

The Republic of Haiti and the Sokoto Caliphate were established in the same year--1804.

From the 15th century onwards, the Atlantic Ocean, once a formidable barrier to trade and travel, became a great highway, directly connecting the west coast of Africa with Europe and with the Americas.

Of all the changes that followed, perhaps the most profound was the transatlantic slave trade.

Unprecedented in scale, lasting almost 350 years, the slave trade tore 12.5 million human beings, ranging from young children to aging adults, away from their families and from their homelands.

Some kingdoms were devastated by the trade.

Others profited from it.

And still others rose in direct opposition to it.

The human cost of the slave trade was horrific and its effects can still be felt to this day.

Even King Garcia II of Kongo had foreshadowed these concerns as early as 1643: "Nothing is more injurious to men than ambition and pride.

"In place of gold, silver, and other things "which serve as money in other places, "the trade and money are pieces, which are not gold or cloth, but creatures."

In spite of the slave trade, but also because of it, African kingdoms would continue to rise and fall.

Over the course of a dynamic 19th century, Africans would witness the rise of one of the most famous warriors in all of the history of the continent.

A global scramble for unprecedented riches would engulf the continent, and one battle would become both something of a last stand against European colonial powers, and yet a beacon of hope for all Africans that a change inevitably would come.

Africa's Great Civilizations is available on Blu-ray and DVD.

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