Trịnh Kiểm (1503-1570) was born to a poor farming family in the village of Sóc Sơn, Vĩnh Ninh, Thanh Hóa (nowadays Vĩnh Lộc, Thanh Hóa Province). Despite not having a proper education, Trịnh Kiểm was exceptionally intelligent and brave. Soon he became a close confidant of the courtier Nguyễn Kim. 
When Nguyễn Kim died, all his power fell into the hands of Trịnh Kiểm who then laid the foundation for the Trịnh’s rule in Đàng Ngoài.