 When Nguyễn Kim was assassinated in 1545, military power fell into the hands of his son-in-law, Trịnh Kiểm.In 1558, Nguyễn Kim's son, Nguyễn Hoàng, suspecting that Trịnh Kiểm might kill him as he had done to his brother to secure power, asked to be governor of the far south provinces around present-day Quảng Bình to Bình Định.Hoang pretended to be insane, so Kiem was fooled into thinking that sending Hoang south was a good move as Hoang would be quickly killed in the lawless border regions.