From 1559 to 1603, Middelburg was the episcopal see of a Catholic bishopric covering all Zeeland. In the Eighty Years' War, Middelburg was captured from the Spanish forces during a long siege (1572–1574). The northern provinces of the original Low Countries won their independence from their former Spanish Habsburg rulers and formed The Netherlands, a Protestant state. Later, in the 17th century (the Dutch Golden Age), Middelburg became, after Holland's metropolis Amsterdam, the most important center for the Dutch East India Company (VOC) in the Republic of the Seven United Netherlands. As such, Middelburg also played an important role in the 17th century slave trade.