Vienna, 1815: First International Condemnation of the Slave Trade

Final Act, Congress of Vienna (Staatsarchiv, Vienna; photograph by Thomas Ledl). By Thomas Ledl (Own work) [CC BY-SA 4.0], via Wikimedia Commons.

In 1814 the main European powers agreed to convene a general congress that should negotiate a long-term peace order by restoring the political landscape of Europe after the Napoleonic Wars. At the Congress of Vienna, which was finally held between September 1814 and June 1815, however, not only European issues were at stake. The peace congress also had a global dimension and can be considered as a cornerstone for the history of humanitarianism. For the first time in history, the representatives of the principal European powers condemned the Atlantic slave trade as contrary to the principles of humanity in the 1815 Vienna Declaration.

The British Foreign Minister Lord Castlereagh, under pressure from the abolitionist movement in his home country, tried to convince the representatives of the other nations who had signed the Peace Treaty of Paris in May 1814—Great Britain, France, Russia, Austria, Prussia, Sweden, Spain, and Portugal—to agree to the international abolition of the Atlantic slave trade. At that time only Denmark (in 1792) and Great Britain and the United States of America (both in 1807) had officially prohibited the international human trafficking with enslaved Africans. Although Castlereagh failed to reach this goal, the representatives of the eight powers finally signed a declaration that was later added as an annex to the final act of the Vienna Congress.

In this Vienna declaration they proclaimed the Atlantic slave trade to be “repugnant to the principles of humanity and universal morality.” In the name of their sovereigns, they declared “the wish of putting an end to a scourge, which has so long desolated Africa, degraded Europe, and afflicted humanity.” The language of the declaration, particularly its reminiscences to European Enlightenment thought and British moral philosophy, is notable. However, it is also notable that the signatories of the Vienna declaration did not proclaim an immediate prohibition of the slave trade (which the British government wanted), but only vaguely declared their intent to do so in the near future. Although other governments were explicitly addressed in the final paragraph of the declaration, and thus the document claimed binding power in terms of international law, it did not say a word about the mode of implementation nor did it set a time limit for the aspired abolition of the slave trade. All this was left to the discretion of the individual states or to be resolved in future negotiations.

The flaw of the declaration in this point clearly was a concession to the colonial interests of Spain, Portugal, and France whose governments did not have the slightest interest in abandoning the lucrative trade at that time. Unsurprisingly, the immediate effects of the declaration were rather weak. Having experienced a sharp drop during the Napoleonic Wars, the Atlantic slave trade rapidly recovered after 1814 and soon reached a similar level to that of the second half of the eighteenth century. There was no significant decrease in the number of slave passages across the Atlantic before the middle of the nineteenth century.

Nevertheless, on the basis of the 1815 Vienna Declaration, which had been signed by the principal colonial powers, British diplomacy did not cease to pressurize the other states in order to extend the abolition of the slave trade on the whole Western world. After the failure of the British efforts to reach a more concrete multilateral solution at the conferences of London in 1816 and Aachen in 1818, Great Britain finally changed its strategy and urged the other powers to sign bilateral treaties by which they consented to a mutual right of visiting suspicious ships in international waters in times of peace. In doing so, the signatory states also had to agree with the establishment of so-called “Mixed Commissions for the Abolition of the Slave Trade”, international courts that should adjudicate the cases of captured slave ships. The first of these bilateral agreements with Great Britain were signed by Portugal and Spain in 1817 and the Netherlands in 1818. By this means, Britain finally achieved to erect a global prohibition that allowed the British navy to implement the international ban on the slave trade more effectively by the 1840s.

Although, at first glance, the Vienna Declaration seemed to have little effect on the practice of the Atlantic slave trade, it clearly was a landmark in the history of humanitarianism. For the first time in history a humanitarian concern was raised into a binding principle of international law. On this basis, a specific enforcement machinery, including military and judicial means, was established and led to the emergence of a treaty-based prohibition regime. Thus, with good reason the Vienna Declaration can be considered a forerunner of the Geneva Conventions on the Abolition of Slavery of 1926 and 1956. It also laid the foundations for the development of other fundamental principles and institutions of international law such as the idea of humanitarian intervention and international tribunals of justice.

Further reading

Although the Vienna Congress is the topic of countless books and articles, most historians focus on its importance for the reshaping of Europe’s political order. The condemnation of the slave trade by the signatories of the Vienna Declaration is an issue that is hardly touched even in recent scholarship. In the last years, however, the growing interest in the history of humanitarianism seems to have led to a change in perspective. For the effects of the Vienna Declaration on the Atlantic slave trade see The Trans-Atlantic Slave Trade Database.

Short Biographical Note on the Contributor:

Thomas Weller is a senior researcher at the Leibniz Institute of European History. His current research focuses, among other topics, on antislavery in the Spanish-speaking world from the sixteenth to the nineteenth centuries.