The transfer of sovereignty of Macau from the Portuguese Republic to the People's Republic of China (PRC) occurred on 20 December 1999. Macau was settled and governed by Portuguese merchants in 1535, during the Ming Dynasty (1368–1644 AD). Portugal's involvement in the region was formally recognized by the Qing in 1749. The Portuguese Governor, emboldened by the First Opium War and the Treaty of Nanking, attempted to annex the territory, expelling Qing authorities in 1846, but was assassinated. After the Second Opium War, the Portuguese government, along with a British representative, signed the Sino-Portuguese Treaty of Peking that gave Portugal sovereignty over Macau, on the condition that Portugal would cooperate with efforts to end the smuggling of opium.