The civil war in between the Lê-Trịnh and Mạc dynasties resulted in 1592, when the military of Trịnh Tùng conquered Hanoi and executed king Mạc Mậu Hợp. Survivors on the Mạc royal loved ones fled to the northern mountains during the province of Cao Bằng and continued to rule there https://vitnam22087.blogocial.com/an-unbiased-view-of-gk88-67033299