International merchants were, of course, the largest sales ventures. They sent representatives to the larger regional/national fairs, but their chief trading occurred elsewhere.
To go back to Charlemagne’s time, a group of Jewish merchants based around the Rhone River traveled the Silk Road regularly. They were called the Radhanites, though it’s unclear why; it might be a Persian term for “those who know the way.” It was through their influence, most likely, that the Khazars converted to Judaism. The Khazar Kingdom was approximately east of modern Ukraine, north of the Black Sea, and it served as one of their resting and trading points between France and India. The Radhanites carried lightweight, high-value things like gems, silk and spices from the east, and often conducted Slavic slaves to those eastern markets. When Sviatoslav of Kyiv destroyed the Khazar Khanate, the road became too dangerous for the Radhanites.
During a long middle period, eastern goods could only be traded at Mediterranean ports, from Muslim merchants who worked the Silk Road. The best way for those goods to travel northward was through the international fairs held in France. Caravans and wagons came overland, up through France, so the big international trade hub was not a port, but instead it was a collection of inland towns that were situated on rivers, midway between Italy and the wool-weaving powerhouse, Flanders. (When I say “overland,” I am including travel by inland river barges.)
The Counts of Champagne, at that time independent from France, nurtured their towns’ fairs by draining swamps and digging canals to make travel from Italy easier. The fairs had regular dates of operation, nearly 7 weeks each, around the year; the towns of Provins and Troyes had two fairs each, while two other towns had one. Whereas small regional fairs (like the goose fairs in England) lasted 3 days and used temporary lodgings, the Champagne Fairs became permanent fixtures with many wooden buildings that turned into international company headquarters. Each fair usually held its cloth market for a number of days, then its leather fair, then the market for “avoir du pois” goods, things sold by weight, opened. These included wax, salt, dye and other chemicals, grain, wine and spices.
Both Muslims and Jews were very active at these international fairs. Leather was imported from Spain (“cordovan” became a synonym for goat leather), and two different red dyes came materials located mainly in Spain. Jews still had a big advantage in international trade, perhaps with some ties lasting from the pre-1100 Radhanite merchants. Their major advantage was that they could travel without carrying large sums of cash, since they had family and business ties with other Jews all over Europe. They gave each other letters of credit, usually in Hebrew. A merchant in Provins might pay a large sum to the bearer of such a letter, and later get paid back by sending an agent with a similar letter to Genoa. This way, sums of gold remained local, guarded from piracy.
The big international fairs had dedicated buildings for currency exchange. During the early heyday of the fairs, counting was done on boards marked with columns, using chips or markers of colored wood that tallied the income. It was a sort of rough abacus. We’ve forgotten how it’s done, but we still call a wide shelf next to the point of sale a “counter.” By the late Middle Ages, all financial professionals had learned the Indian-Arabic numeral system’s columns and were keeping books with debit and credit entries. I don’t know how they calculated rates of currency exchange, but the first specialists worked out those principles right there in Champagne.
Needless to say, every action above a sneeze was also taxed. Eventually, an heiress in Champagne married the King of France, who greedily seized the golden goose and began to squeeze. Yes, the counts had received heavy taxes from the fairs, but they had kept within traditional boundaries that permitted profit. Under the new regime, the profit margin shrank, and the fairs quickly collapsed. Merchants began just selling their wholesale goods directly in cities like London. Ships, especially from Venice and the Baltic Sea, took over the task from the inland routes and canals. Ship-building increased rapidly, and Europe was set for the age of exploration.