Nguyễn Kim
Meanwhile, Nguyễn Kim, a former official in the Lê court, revolted against the Mạc and helped king Lê Trang Tông restore the Lê court in the Thanh Hóa area. Thus a civil war began between the Northern Court (Mạc) and the Southern Court (Restored Lê). Nguyễn Kim's side controlled the southern part of Annam (from Thanhhoa to the south), leaving the north (including Đông Kinh-Hanoi) under Mạc control. 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. Hoàng pretended to be insane, so Kiểm was fooled into thinking that sending Hoàng south was a good move as Hoàng would be quickly killed in the lawless border regions. However, Hoàng governed the south effectively while Trịnh Kiểm, and then his son Trịnh Tùng, carried on the war against the Mạc. Nguyễn Hoàng sent money and soldiers north to help the war but gradually he became more and more independent, transforming their realm's economic fortunes by turning it into an international trading post.