In 1527, a high-rank military officer of the weakened court, Mạc Đăng Dung, seized power of Đại Việt.

[4] Envoys were sent to Ming China in 1536 and 1537 to denounce Mạc Đăng Dung as a usurper and to request an intervention aid in restoring the legitimate dynasty.

This effort continued through most of the sixteenth century, and in the course of the long seesaw struggle with the Mạc, a rivalry emerged between the two families, represented by their principal figures, Nguyễn Kim and Trịnh Kiểm (1503–1570).

Through his sister, Kiểm's wife, Hoàng requested that he be appointed governor general of the distant southern frontier territories of Thuận Hoá and Quảng Nam.

Shortly thereafter, in 1558, Nguyễn Hoàng entered the southern realms, marking the beginnings of a political division that would have lasted for 250 years.