鄭檢
In 1545, Nguyễn Kim was poisoned by Dương Chấp Nhất, a surrendered general of the Mạc dynasty. The power of royal court was then passed to Nguyễn Kim's son-in-law [[Trịnh Kiểm]] who became the founder of the [[Trịnh lords]]. Since then the emperor has only become a figurehead, Trịnh Kiểm and his successors were the "[[de facto]]" rulers of the country and continue the war with the Mạc. The war has three actual fighting periods: 1533–1537, 1551–1564 and 1584–1592. During the early confront period, the Lê dynasty introduced personnel firearm like matchlocks into their army and surprised the Mạc army.