The Jiajing wokou raids caused extensive damage to the coast of China in the 16th century, during the reign of the Jiajing Emperor (r. 1521–67) in the Ming dynasty. The term "wokou" originally referred to Japanese pirates who crossed the sea and raided Korea and China; however, by the mid-Ming, the wokou consisted of multinational crewmen that included the Japanese and the Portuguese, but a great majority of them were Chinese instead. Mid-Ming wokou activity began to pose a serious problem in the 1540s, reached its peak in 1555, and subsided by 1567, with the extent of the destruction spreading across the coastal regions of Jiangnan, Zhejiang, Fujian, and Guangdong.