In 1833, the parliament of Great Britain passed 3 & 4 William IV c.73: “An Act for the Abolition of Slavery throughout the British Colonies; for promoting the Industry of the manumitted Slaves; and for compensating the Persons hitherto entitled to the Services of such Slaves” [1]. This came at the price of a £20,000,000-mountain of debt [2]. Perhaps peanuts in today’s money, the pound was once issued to have the value of a literal pound’s weight of silver sterling, although the Napoleonic Wars caused a silver shortage, with the government redefining the pound in 1816 to be an amount of gold of similar value. This £20,000,000 was the equivalent of 40% of the nation’s budget for that year [2], and the interest was of sufficient magnitude such that the bill was only repaid in 2014 [2], meaning that most taxpayers alive in Britain today have paid personally for the abolitionist cause.
The treasury tweeted about this in 2015 [3]:
The reaction? Uproar that the money didn’t go to the slaves [3], and the deletion of the tweet. You can put yourself into generations of debt to pay for the freedom of slaves that you didn’t even kidnap, and it will be twisted into an episode of villainy. This wasn’t all that Great Britain did about the issue either. An earlier act banned the trade of slaves in the empire in 1807 [4], and a comparable amount was spent on enforcement [5, p.43; & 6, p.437], with the West Africa Squadron being established to patrol the African coastline and execute slave traffickers for the capital offense of engaging in “piracy”.
The yearly enforcement expenses are as follows [5, p.43]:
The expenses for each year (in millions of 1821-1825 pounds) are as follows:
1816: 0.5808510638297870 1833: 0.1510638297872340 1850: 0.536170212765957
1817: 0.0787234042553192 1834: 0.1425531914893620 1851: 0.4446808510638300
1818: 0.6000000000000000 1835: 0.1297872340425530 1852: 0.3872340425531910
1819: 0.2404255319148940 1836: 0.1723404255319150 1853: 0.2319148936170210
1820: 0.2234042553191490 1837: 0.1914893617021280 1854: 0.1680851063829790
1821: 0.1936170212765960 1838: 0.1936170212765960 1855: 0.1659574468085110
1822: 0.1744680851063830 1839: 0.1936170212765960 1856: 0.1872340425531910
1823: 0.1404255319148940 1840: 0.1255319148936170 1857: 0.2595744680851060
1824: 0.1553191489361700 1841: 0.1787234042553190 1858: 0.3489361702127660
1825: 0.1234042553191490 1842: 0.1617021276595740 1859: 0.2553191489361700
1826: 0.1297872340425530 1843: 0.2361702127659570 1860: 0.2361702127659570
1827: 0.1787234042553190 1844: 0.3765957446808510 1861: 0.2361702127659570
1828: 0.1361702127659570 1845: 0.4957446808510640 1862: 0.2617021276595740
1829: 0.1765957446808510 1846: 0.4446808510638300 1863: 0.2276595744680850
1830: 0.2319148936170210 1847: 0.4489361702127660 1864: 0.2170212765957450
1831: 0.1148936170212770 1848: 0.5000000000000000 1865: 0.2340425531914890
1832: 0.1361702127659570 1849: 0.5127659574468090
Estimated by counting pixel heights in the line graph.
This comes up to a yearly expense of £258,532.4, or £12,668,090 in total. Assuming the same spending from 1807 to 1816, this would be £14,994,880 in total, which given 6.74% deflation from 1823 to 1833 would be a total of £13,984,230. Another existing estimate puts it as high as £40,000,000 [6, p.437].
Although the 1807 ban initially applied only to British vessels, Britain also employed diplomatic and economic pressure to get other countries to either enforce their own bans or allow the Royal Navy to police their ships [7, xxi, xxxiii–xxxiv]. From 1807 to 1860, the Royal Navy seized ~1600 slave ships and directly freed the ~160,000 slaves aboard them [6, p.433]. There’s also the matter however many people would have been enslaved later on if trade had not been disrupted.
The Barbary Slave Trade:
This isn’t the only slave trade Great Britain fought against. Over the course of the 16th, 17th, and 18th centuries, the North African Ottoman Barbary states of Algeria, Tripolitania, and Tunisia waged a campaign of kidnapping and enslaving people from across the coastlines of Europe. Towards the onset of the campaign in the early 17th century, the English navy was in a deteriorated state, but the British coastline and Irish sea became such notorious targets that this became the impetus for the Navy’s restoration. Between 1606 and 1616, the Royal Navy admitted to the capture of 466 ships [8]. The situation only began to change following the end of the English civil war when the Royal Navy was built up under Oliver Cromwell. By 1700, the Corsairs generally knew better than to harass the British aisles for slaves. It was in commemoration of this triumph that in 1740, James Thompson wrote Rule Britannia:
When Britain first, at heaven's command,
Arose from out the azure main,
Arose arose from out the azure main,
This was the charter, the charter of the land,
And Guardian Angels sang this strain:
Rule, Britannia! Britannia, rule the waves!
Britons never, never, never will be slaves.
Rule, Britannia! Britannia, rule the waves!
Britons never, never, never will be slaves.
Still more majestic shalt thou rise,
More dreadful from each foreign stroke,
More dreadful, dreadful from each foreign stroke,
As the loud blast that tears the skies
Serves but to root thy native oak.
Rule, Britannia! Britannia, rule the waves!
Britons never, never, never will be slaves.
Rule, Britannia! Britannia, rule the waves!
Britons never, never, never will be slaves.
Thee haughty tyrants ne'er shall tame;
All their attempts to bend thee down
All their, all their attempts to bend thee down
Will but arouse, arouse thy generous flame,
But work their woe and thy renown.
Rule, Britannia! Britannia, rule the waves!
Britons never, never, never will be slaves.
Rule, Britannia! Britannia, rule the waves!
Britons never, never, never will be slaves.
The Muses, with freedom found,
Shall to thy happy coasts repair.
Shall to thy happy, happy coasts repair.
Blest isle! with matchless,
With matchless beauty crowned,
And manly hearts to guard the fair.
Rule, Britannia! Britannia, rule the waves!
Britons never, never, never will be slaves.
Rule, Britannia! Britannia, rule the waves!
Britons never, never, never will be slaves.
How many Europeans were kidnapped into slavery over this time? The best estimate of the total number European slaves there would be across the Barbary regencies in any given year is about 35,000 [8]; these were 90% men (who were totally barred access to women), and by Davis’ estimation, 20% of this population would die per year, meaning this would need to be replaced with new captures. Such figures are most applicable to the period of 1580 to 1680 at the height of the the raids, having slowly ramped up beforehand and declined afterwards until the European slave population was barely 500 in the 1790s and then flared up again during the disorder of the Napoleonic wars and then collapsing again for good. For this 100-year period then, with 7000 yearly captures to make up for attrition, this would add up to 700,000 Europeans being kidnapped in total across the century.
Really though, this 20% attrition rate is indefensibly low. When the effects of plague are counted, European slaves in Tripoli had an annual mortality rate of 46% across the 100-year period, and on a per-plague basis, this should be worse in algiers due to greater population density, which would apply to 30k of the 35k slaves, and Algiers also had more such plagues per decade. Just rolling with the already-conservative Tripolitanian mortality, you'd also have to increase the attrition rate by 3% to account for ransoms and escapees. So the bare minimum annual attrition rate should be 50%, and when replacing them, some would die on the journey, so for every 17.5k replacements you'd have to capture more people than that. Just going with 17.5k per year, this would be 1,750,000 across the century. Additionally, of the survivors, it seems about ~14%-28% would convert to islam and eventually be freed from slavery, but that's a life-long effect rather than an annual effect, so by this Davis’ estimate, it's an additional ~3%-4% per year.
The dude's plague adjustment is also retarded. He arrives at 2% annual plague attrition by averaging plague deaths across years when the 46% figure is the result of already doing (and doing so in a lower-density area which should have abnormally-low plague mortality).
The raids actually lasted in total for a period of about 250 years but at a lower rate during the periphery than the core 100-year period, so maybe 2,000,000 across the entire 250-year period might be reasonable. Across the entire region, a 60% attrition rate would actually still be defensible and probably even still a bit conservative, by which it might be 2,400,000 Europeans kidnapped into slavery.
References:
Henry, W. IV. (1833). 1833: 3 & 4 William 4 c.73: An Act for the Abolition of Slavery throughout the British Colonies; for promoting the Industry of the manumitted Slaves; and for compensating the Persons hitherto entitled to the Services of such Slaves. In THE STATUTES OF THE UNITED KINGDOM OF GREAT BRITAIN AND IRELAND, 3 & 4 WILLIAM IV. 1833. His Majesty’s Printers. Retrieved from https://statutes.org.uk/site/the-statutes/nineteenth-century/1833-3-4-william-4-c-73-abolition-of-slavery-act/
Information Rights Unit. (2018). Freedom of Information Act 2000: Slavery Abolition Act 1833. HM Treasury FOI2018/00186. Retrieved from https://assets.publishing.service.gov.uk/media/5a7d78a6e5274a676d53243f/FOI2018-00186_-_Slavery_Abolition_Act_1833_-_pdf_for_disclosure_log__003_.pdf
Olusoga, D. (2018). The Treasury’s tweet shows slavery is still misunderstood. The Guardian. Retrieved from https://www.theguardian.com/commentisfree/2018/feb/12/treasury-tweet-slavery-compensate-slave-owners
Hanover, G. III. (1807). 1807: 47 George 3 session 1 c.36: An Act for the Abolition of the Slave Trade. Retrieved from https://statutes.org.uk/site/the-statutes/nineteenth-century/1807-47-geo-3-1-c36-slave-trade/
Huzzey, R. (2017). Freedom burning: anti-slavery and empire in Victorian Britain. Cornell University Press. Retrieved from https://not-equal.org/content/pdf/misc/Huzzey2012_FreedomBurning.pdf
Rees, S. (2009). Sweet water and bitter: the ships that stopped the slave trade. Random House. As cited in Sullivan, A. (2020). Britain's War Against the Slave Trade: The Operations of the Royal Navy's West Africa Squadron 1807–1867. Frontline Books. Retrieved from https://not-equal.org/content/pdf/misc/Sullivan2020.pdf
Falola, T., & Warnock, A. (2007). Encyclopedia of the Middle Passage: Greenwood Milestones in African American History. Bloomsbury Publishing USA. Retrieved from https://not-equal.org/content/pdf/misc/Falola2007.pdf
Davis, R. C. (2001). Counting European slaves on the Barbary coast. Past & Present, (172), 87-124. Retrieved from https://sci-hub.ru/https://doi.org/10.2307/3600777
"these were 90% men (who were totally barred access to women)"
Giles Milton's 'White Gold' is a good account of the Barbary trade. It centres on the ordeal of the Cornishman Thomas Pellow as slave to successive sultans of Morocco in the 18th century.
Among other things it recounts is the interesting detail that Sultan Moulay Ismael was at least half subsaharan African. He forced all white slaves whom he favoured with matrimonial rights (a minority, courtiers and some overseers, I think) into unions with black women, though Pellow was excepted on a whim and allowed to marry a white(r) woman. The point is that Moulay Ismael had a shrewd pre-scientific understanding of heredity: he believed that the issue of white-black unions made superior slaves.
Major self own