From the 13th century, the merchant cities of the Hanseatic League monopolized the lucrative Baltic trade in grain, timber, amber and iron. League members Lübeck and Danzig were also the major ship-building centres of the time. In the second half of the 16th century, the trade grew as nation states like France and England became ever-expanding markets, but the developing nation states rimming the Baltic also threatened mercantile dominance. In 1563, war broke out between belligerent new Swedish and Danish kings; confusingly, Sweden and Denmark were simultaneously allies with the Poland-Lithuania Commonwealth against Russia over control of Lithuania. Russia seized the Hanse ports of Narva and Dorpat, while Denmark expelled their merchants from Danish-held Bergen (1559). The conflicts tested the mental health of the monarchs involved. Both Eric of Sweden and Ivan of Russia went insane; Eric was deposed, Ivan recovered (arguably) to earn the epithet ‘Terrible’.
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