For some 75 years, historians have argued about the role that slavery and colonialism played in industrialisation. The key work on this subject was published in 1944 by the historian Eric Williams, who, significantly, came from the Caribbean and earned his doctorate at Oxford. His hotly disputed thesis that the slave trade and colonial goods mass-produced by slaves, such as sugar, coffee and tobacco, provided the capital for the new coal mines and textile factories, has found new appreciation in the course of debates on post-colonialism. At least for the beginning of the Industrial Revolution in England, concrete connections have now been proven: English traders trafficked some 2.5 million people from Africa to the plantations of the Caribbean and North America in the 18th century - more than any other nation. Proceeds from this flowed into the expanding industrial districts of northern England and Wales. In the industrialisation of Germany in the 19th century, profits from the colonial sugar trade contributed to the development of the railway network and the motorisation of factory production - even before the country itself acquired colonies. But whether such investments were crucial to the emergence of the capitalist factory economy is not yet clear.

Colonial powers such as France and Portugal also shipped millions of Africans across the Atlantic and Indian Oceans to the highly profitable sugar cane plantations of their colonies, but industrialisation did not begin there until the mid-19th century or later. A direct link is therefore difficult to discern, but there too the immense influx of capital from the slave economy in the 18th century boosted the economy. Two economic historians have published one of the few detailed studies of the Netherlands: According to them, business with colonial goods from America accounted for about 20% of total Dutch foreign trade around 1770.

It was not only trade and shipbuilding in the major ports that made money from the import of colonial goods, but also banks and insurance companies, as well as inland industries that processed imported goods: Sugar refineries, tobacco factories and coffee houses boomed throughout Europe, and Swiss confectioners were considered masters in the processing of cocoa and spices from overseas.

Exports were also quite lucrative for European countries: a German historian calculates that, at the end of the 18th century, Prussia earned at least 15% of its foreign trade profits from the export of linen for the slave trade. In the Caribbean colonies, the durable fabric was used to clothe slaves, and on the west coast of Africa, traders exchanged white linen from Silesia for slaves.

Another sought-after commodity was brass, which could not be made in Africa because of the lack of zinc. As early as the 16th century, Portuguese merchants had millions of brass bracelets made in the German Rhineland to pay for the slaves supplied to them by the kings of Benin. The slave ships also carried export goods such as rifles, tobacco pipes and, last but not least, "Indiennes", colourfully printed cotton fabrics that also came from deep in the interior: Switzerland. The risky but lucrative triangular trade between Africa, the colonies and Europe can be seen as an early form of globalisation that captured large parts of the European economy and created capital for later industrialisation.

The industries then contributed decisively to the next wave of colonialism in the late 19th century. This created a huge demand in later industrial nations such as France and the Netherlands: the colonies were needed as suppliers of raw materials for production and as markets for the products. Great Britain, a leading industrial nation as well as a colonial power, provided the prime example: raw cotton was imported from the Indian colony, then the local market was flooded with machine-woven fabrics, ruining the centuries-old Indian textile industry. Instead of sugar and coffee as consumer goods, European entrepreneurs now imported huge quantities of cotton, largely from the rapidly expanding slave plantations in the southern states of the USA. In addition, ores and agricultural products came from the colonies to supply the new industrial cities. Towards the end of the century, demand diversified as the electrical engineering, chemical and mechanical engineering sectors expanded in the "Second Industrial Revolution": copper, for example, came from the Belgian Congo, crude oil from Dutch Java, rubber for rubber production from French Indochina. Behind the imperialist sabre-rattling of the powerful industrial nations, which increasingly rivalled aggressively for colonies, were the needs of the dominant industries.

Industrialisation also changed the ideological side of colonialism: in 1807, England banned the slave trade, and in 1833 it also largely banned slavery - not as the first, but as the nation that could halfway enforce this decision worldwide thanks to its superior navy. Great influence on the ban was exerted by a morally based public movement in Britain, predominantly supported by evangelicals. But slavery no longer fit the times economically either: capitalism demanded a different image of the world of work, based on the ideas of self-responsibility and the market economy. This meant the concept of the "free worker" instead of the slave economy and free trade instead of customs monopolies and trade restrictions. Historian Eric Williams therefore believed that British factory owners and merchant entrepreneurs joined forces with philanthropists to bring about the end of slavery and free trade at the same time. Scholars still argue about how correctly he described the complex historical processes in England. But he got to the heart of the logic of the new era: slavery had to be banned in order to raise the status of industrial workers. Even if they had to work 12 hours a day, received miserable wages and lived in damp mass quarters - they were not slaves, they were "free". This was the ideological legitimisation that industrialised mass society needed.