From the thirteenth century onward, Pomerania had been a major grain-producing market. But the arrival of the Black Death not only caused the population to plummet, it also drove large numbers of farmers to migrate to Prussia and Poland, gradually turning those two countries into major grain-production centers.
After the Battle of Grunwald in 1410, thousands of soldiers fought for seven hours before finally freeing Prussia from the control of the Teutonic Knights, allowing Danzig on the banks of the Vistula River to develop.
By 1464, Danzig no longer faced tariff barriers, and local commerce flourished rapidly. Until the outbreak of the Thirty Years' War, its grain exports reached 200,000 tons. Later, it and Lübeck both became centers of the Hanseatic League.
In the Mediterranean, anything worth transporting by ship was extremely valuable, to the point where shipping costs were negligible compared with its sale price.
But if grain was transported by ships crossing the Mediterranean, its price would generally rise around fourfold. Like the heroes in Ancient Greek legends who sailed to Troy to reclaim Helen, they sometimes encountered windless weather, so Mediterranean merchant ships of that era needed oars as well as sails.
The North Sea and the Baltic Sea, meanwhile, never lacked wind. The cogs used by the Hanseatic League not only had tremendous carrying capacity, but could also be handled by just a few sailors. Compared with the value of their cargo, transport costs were negligible.
Besides climatic conditions, war also adversely affected Europe's grain market. Grain that should have been harvested was left in the fields because the farmers had fled. Some hoped to return and resume farming after the war, while others simply settled elsewhere.
Portugal and Spain did not rely on Hanseatic League grain. They traded with the Ottoman Empire, and unless something