 Northern and Southern Vietnam was a fluid concept that changed constantly during the course of history.During the Lê–Mạc wars (1541–92), Vietnam was partitioned with the Mạc dynasty holding the Red River Delta and Lê dynasty controlling the Central Region from Nghệ An to Bình Định while Champa and the Khmers still held their polities further south.During the Trịnh–Nguyễn War (1627–73), the country was partitioned between two ruling Lords with the border being the Gianh River in Quảng Bình Province.