The initially small population of Portuguese merchants rapidly became a growing city. The Roman Catholic Diocese of Macau was created in 1576, and by 1583, the Senate had been established to handle municipal affairs for the growing settlement. Macau was at the peak of its prosperity as a major entrepôt during the late 16th century, providing a crucial connection in exporting Chinese silk to Japan during the "Nanban" trade period. Although the Portuguese were initially prohibited from fortifying Macau or stockpiling weapons, the Fortaleza do Monte was constructed in response to frequent Dutch naval incursions. The Dutch attempted to take the city in the 1622 Battle of Macau, but were repelled successfully by the Portuguese. Macau entered a period of decline in the 1640s following a series of catastrophic events for the burgeoning colony: Portuguese access to trade routes was irreparably severed when Japan halted trade in 1639, Portugal revolted against Spain in 1640, and Malacca fell to the Dutch in 1641.