Latest / The Atlantic Slave Trade: Empire Built on Human Suffering — Fexingo History / The 1820 Treaty That Made the Slave Trade Piracy
Transcript
- Luna: We've talked a lot about the horrors of the Middle Passage, the revolts, the forts. But I'm curious—when did the major powers actually start treating the slave trade as a crime? Lucas: Great question. The big turning point came in 1820, when the United States and Britain signed the Treaty of London. Both countries agreed to declare the international slave trade an act of piracy—punishable by death. It was the first time two major naval powers explicitly criminalized the trade on the high seas. Lucas: Now, Britain had already abolished its slave trade in 1807 and was pressuring other nations to follow. At the Congress of Vienna in 1815, the British pushed for a joint declaration against the trade. But it took years of diplomatic wrangling to get the U.S. on board. Luna: What changed in 1820 to make the U.S. finally agree? Lucas: A few things. President James Monroe and his Secretary of State John Quincy Adams were both opposed to the slave trade, but they had to balance southern slaveholding interests. The British offered a compromise: they wouldn't interfere with America's domestic slave trade, but they wanted mutual search rights to stop slave ships on the ocean. The U.S. was wary of Britain boarding American vessels—memories of impressment from the War of 1812 were still fresh. Lucas: So the treaty was carefully worded. It allowed each nation's warships to search vessels flying the other's flag if they suspected slaving. And it set up mixed commission courts in Sierra Leone, Brazil, and elsewhere to adjudicate captured ships. If found guilty, the captain and crew could face the death penalty. Luna: That sounds like a huge step forward. Did it actually work? Lucas: It worked—but only up to a point. The treaty made the trade illegal on paper, but enforcement was incredibly difficult. The U.S. sent a small squadron to the African coast, the Africa Squadron, which started with just a few ships. They were up against fast Baltimore clippers built specifically to outrun naval patrols. And many slavers simply flew false flags—Spanish, Portuguese, French—to avoid search. Lucas: One of the early commanders of the Africa Squadron was a young Captain Matthew C. Perry—yes, the same Perry who later opened Japan. He wrote detailed reports about the challenges of intercepting slavers. In one letter, he described chasing a Brazilian schooner for two days before finally catching it off the coast of Cape Verde. Luna: Perry was involved in this? I only know him from Japan. Lucas: Exactly. He was a committed abolitionist in his own way. He saw the slave trade as a barbaric practice that tarnished the nation's honor. But even he couldn't stop the flood. Between 1820 and 1860, an estimated one million enslaved Africans were still transported illegally, mostly to Brazil and Cuba. The treaty was more of a moral statement than a practical solution. Luna: So the death penalty for slavers—was anyone actually executed? Lucas: Surprisingly few. The mixed commission courts often convicted the ship, not the crew. Captains would argue they were just following orders, or that they were forced into the trade by financial pressures. And the courts themselves were underfunded, understaffed, and often corrupt. In Sierra Leone, the court had a backlog of cases that took years to resolve. Lucas: There's also a darker side to this story. When a slave ship was captured, the enslaved people on board weren't automatically freed. They were classified as 'recaptives' and handed over to local authorities—often to be apprenticed or resettled. In some cases, they ended up in conditions not much better than slavery. The British established a settlement in Sierra Leone for recaptives, but it was overcrowded and disease-ridden. Lucas: And the U.S. had its own shameful policy. The 1819 Act in Addition to the Acts Prohibiting the Slave Trade allowed the president to return recaptives to Africa, but the government often sold them at auction in the United States. That's right—the U.S. government itself profited from the sale of people it had 'rescued' from the slave trade. Luna: Wait, the U.S. government sold recaptives into slavery? That's appalling. Lucas: It is. And it shows how deeply embedded the institution was. The treaty was a step forward in international law, but it couldn't overcome the economic and racial realities of the time. Still, it set a precedent. By declaring the slave trade piracy, Britain and the U.S. laid the groundwork for later treaties and eventually the total abolition of slavery in the Western Hemisphere. Lucas: If today's episode gave you a new perspective on how hard it was to end the slave trade, the way we keep these conversations going without ads is listener support. You can help at buy me a coffee dot com slash fexingo. Luna: Yeah, it's such a small thing, but it really does keep the show independent and ad-free. Lucas: So to come back to the treaty—one of its most lasting legacies was the idea that the slave trade was a crime against humanity. That concept didn't fully emerge until the 19th century, but the 1820 treaty was a crucial moment. It forced nations to publicly condemn an institution they had once embraced. Luna: I'm also thinking about the irony: the same country that signed the treaty—the U.S.—allowed slavery to flourish for another forty-five years. The treaty only covered the international trade, not the domestic one. Lucas: Exactly. That's the crucial caveat. The British had already abolished their own slave trade, so for them it was about stopping others. For the U.S., it was a compromise: we'll stop importing new slaves from Africa, but we won't interfere with the buying and selling of slaves already here. That's why the treaty was palatable to southern states. Lucas: And the enforcement gap meant that illegal slavers adapted. They started using faster ships, like the famous Baltimore clippers. They would also land enslaved people on the coast of Cuba or Brazil under cover of night, then destroy the evidence. The treaty was a legal landmark, but on the water, the battle was far from over. Luna: So the Africa Squadron—how effective was it really? Lucas: Historians give it mixed reviews. At its peak in the 1850s, the squadron had about a dozen ships patrolling thousands of miles of coastline. They captured around 100 slave ships and freed some 5,000 enslaved people. But compared to the estimated 10,000 ships that successfully ran the blockade, it was a drop in the ocean. Lucas: The British Royal Navy was much more aggressive. They had a larger fleet and were more willing to board foreign vessels, even without permission. By the 1840s, the British had a network of treaties with Spain, Portugal, and Brazil that allowed mutual search. The U.S. treaty was narrower, but it did allow for some cooperation. Lucas: One case that illustrates the tension: in 1839, the U.S. schooner Grampus captured the Spanish slave ship Amistad off the coast of New York. Wait—actually no, that's the famous Amistad case, but it wasn't the Grampus. That was a different incident. Let me correct myself: the Grampus was an American warship that captured a slaver called the Fenix in 1837. The enslaved people on board were taken to Charleston and sold. Luna: Sold in Charleston? After being rescued by the U.S. Navy? Lucas: Yes. The Navy was supposed to send them to Africa, but the local courts in South Carolina ruled they were property under state law. So the U.S. government auctioned them off. It's a stark reminder that the treaty existed in a legal limbo—federal law and state law could contradict each other. Lucas: The treaty also had a strange afterlife. After the Civil War, the U.S. finally ratified a broader treaty with Britain in 1862 that allowed for mutual search in African waters. That one was more effective, but by then the slave trade was already collapsing under the weight of abolitionist pressure and the end of the Civil War. Luna: So the 1820 treaty was more of a symbolic start than a practical end? Lucas: Exactly right. It was a crucial moral and legal shift—the first time two major powers called the slave trade piracy. But without strong enforcement, it was like passing a law against speeding with no police on the road. Still, it mattered. It gave abolitionists a legal foothold and set the stage for the eventual destruction of the transatlantic slave trade.