In 1419 the town controlled a monopoly in producing a special cloth - fustian; therefore, all manufacturers of this cloth in Hungary had to move to Kosice. Ten years later, Kosice also gained a monopoly of bleaching flax linen, which was shared with Bardejov.
During the turbulent years of the struggle for the Hungarian throne, Kosice played an important role. At the end of the first half of the 15th century, under the leadership of Jan Jiskra of Branděs (who was an Ispan, an administrator of Saris County, with its center in Kosice) expeditions were undertaken against the Poles and Hungarians. Loans for these expeditions flowed out of Kosice's municipal treasury. All of the "Estates of the Tisza Region" submitted to Jiskra at the Diet of Seňa in 1445; Jan Talafus became a captain of Kosice. The reformist Hussites retained their power over the town after the peace had been signed with Janos Hunyadi in 1450; they lost it only after their defeat at Sarissky Potok.
The patricians of the town originated from the merchant class at that period. Crafts and agricultural production had little significance apart from viticulture. The mass migration of people - especially Hungarian aristocracy - from the southern territories of the kingdom occupied by the Turks resulted in an enormous concentration of population within the town walls; the number reached 7,000. At the time when Buda was seized and occupied by the Turks, Kosice became the capital of the Hungarian kingdom for some time.
In the mid-16th century a great fire almost destroyed the whole town. It damaged St. Elizabeth's as well as the town walls. Owing to the support of the royal court, a new Renaissance town arose on the ruins of the old one. During the reconstruction works, the vacant ground, which had remained on the building plots, especially behind the houses, was built up with additional buildings with the purpose of housing the rising population.
