Nagasaki Prefecture is a prefecture of Japan located on the island of Kyushu. The capital is the city of Nagasaki. Nagasaki Prefecture was created by merging of the western half of the former province of Hizen with the island provinces of Tsushima and Iki. Facing China and Korea, the region around Hirado was a traditional center for both traders and pirates. During the 16th century, Catholic missionaries and traders from Portugal arrived and became active in Hirado and Nagasaki, which became a major center for foreign trade. After being given free rein in Oda Nobunaga's period, the missionaries were forced out little by little, until finally, in the Tokugawa era, Christianity was banned under the Sakoku national isolation policy, during which time, Japanese foreign trade was restricted to Chinese and Dutch traders based at Dejima in Nagasaki; however, Kirishitan worship continued underground.