In 1944, an Australian soldier named Maurie Isenberg was posted to a radar station on Marchinbar Island, in the Wessel Islands off the far north coast of Australia. In his spare time he went fishing. One day, in the sand just below the high-water mark, he noticed a few small, green, round objects. He picked them up, found a few more nearby, and put them in a tin.
The tin stayed in his kit for 35 years. In 1979 he finally had the coins identified. Four were Dutch East India Company coins. The other five were copper coins from the Sultanate of Kilwa, an island city off the coast of what is now southern Tanzania, on the other side of the Indian Ocean.
Nobody knows for certain how they got there. The Powerhouse Museum in Sydney, which holds them today, thinks they are most likely linked to later Portuguese voyages, but it is still a mystery.
What is not a mystery is why Kilwa had coins to lose.
The city at the gate
Kilwa Kisiwani was lived in from the ninth to the nineteenth century, and it reached its peak in the thirteenth and fourteenth. UNESCO, which made its ruins a World Heritage Site in 1981, describes it as a Swahili trading city whose prosperity rested on control of the Indian Ocean trade with Arabia, India and China. Gold and ivory from the interior went out. Silver, carnelians, perfumes, Persian faience and Chinese porcelain came in. Kilwa minted its own coins between the eleventh and fourteenth centuries.
When the Moroccan traveller Ibn Battuta stopped there in 1331, he was impressed. "Kilwa is one of the most beautiful and well-constructed towns in the world," he wrote. "The whole of it is elegantly built."
The ruins still show why. The Great Mosque, built of coral stone and lime mortar, is the oldest standing mosque on the East African coast. Its great dome, from the thirteenth century, was the largest in East Africa until the nineteenth. On a bluff above the sea stand the remains of Husuni Kubwa, a palace built between about 1310 and 1333, with more than a hundred rooms and a large octagonal bathing pool. Archaeologists believe its great courtyard was a place where merchants rested and goods were stored before being loaded onto dhows.
This was a confident, cosmopolitan, wealthy city. And most of that wealth rested on one thing.
Gold it never mined
The gold did not come from Kilwa. It came from the interior of southern Africa, the world of Great Zimbabwe, and was carried to the port of Sofala, in what is now Mozambique.
Kilwa's genius was to put itself in the middle of that flow. According to National Geographic's account of the city's history, Kilwa's rulers extended their influence south until Sofala became their outpost. From the late 1200s, under the Mahdali dynasty, they kept consolidating until the East African gold trade came under Kilwa's control.
Geography helped. As one study of mining and African cities explains, the monsoon winds further south were too weak for the large ocean-going ships. So gold moved north from Sofala in smaller boats to Kilwa, where it was loaded onto bigger vessels bound for the markets of the Middle East and India. Kilwa sat at the gate.
When the route moved
A business built on someone else's flow lasts as long as the flow.
Historians point to several pressures. The same study links the end of Kilwa's great age, after about 1350, to falling gold production in Zimbabwe. Some scholars also point to falling gold prices. None of these happened on the island. All of them hit it.
Then came the Portuguese. They reached East Africa in 1498 and wanted the gold trade for themselves. To them, Sofala was the focal point: control it, and you control the gold. In 1505 Francisco de Almeida occupied Kilwa after it refused to pay tribute, and the Portuguese built a fort there. They held it only until 1512. But the damage was done. Kilwa slowly declined and was abandoned by the middle of the nineteenth century.
There is a twist. The Portuguese plan to take over the gold trade did not work well either. Historians of the Sofala coast note that, even with forts, trading posts and licences, the system proved ineffective, partly because the newcomers did not understand the networks they were trying to control. Owning the gate turned out to be harder than taking it.
Today Kilwa's ruins are fragile. From 2004 to 2014 UNESCO kept them on its List of World Heritage in Danger, threatened by the sea, vegetation and new building.
The lesson for enterprise and industry
Kilwa was not foolish. It was excellent at what it did: the harbour, the ships, the merchants, the coins, the buildings. But its greatest asset was its position, standing where someone else's product passed. Positions can be taken.
Many companies today are Kilwas without knowing it. A distributor that lives on one brand's contract. A factory that sells most of its output to one buyer. A processor that depends on a single source for its main raw material. A software business that lives or dies on one platform's rules. The middle can be a good place to stand, as long as you know you are standing there.
Kilwa's story suggests three questions.
Where does your value really come from? Draw the flow: inputs, suppliers, channels, customers. Mark every point where one name carries most of the weight. That is your Sofala.
What do you own that would move with you? Kilwa's palace could not follow the gold. Capabilities can: skills, process know-how, good records, relationships, a product customers choose for its own sake. A location, a licence or a single contract cannot.
Are you watching the source, or only the counter? From the island, Kilwa could see the gold arriving. It could not easily see the mines slowing hundreds of kilometres inland. Real visibility means looking earlier in the chain, at supplier performance, intake quality and changing demand, before problems show up in revenue.
Five copper coins in a Sydney museum show how far Kilwa's reach once went. The ruins on the island show that reach is not the same as roots.
So here is my question for every founder, manager and plant team:
If the route through your business moved tomorrow, what would still be yours?
Sources: UNESCO World Heritage Centre, Ruins of Kilwa Kisiwani and Ruins of Songo Mnara; Ibn Battuta, Travels (trans. Gibb), via Teaching Medieval Slavery and Captivity; Powerhouse Collection, Sydney: Kilwa and Dutch coins from Marchinbar Island; Indiana University: search for the Wessel Islands coins (2013); National Geographic, This abandoned East African city once controlled the medieval gold trade; Encyclopaedia Britannica, Kilwa; Eureka and beyond: mining's impact on African urbanisation (2012); The Sofala Coast (Mozambique) in the 16th Century (OpenEdition); Nakamura, Hidden Cultural Heritage: Kilwa Island (Minpaku).