English: Map of China during the period of transition from the Sui to the Tang, with the major regional rulers and contenders for the throne, and the main military activities of the Tang (in red) and their various rivals (in purple). Geophysical map taken from DEMIS Mapserver, which are public domain, other wise self-made. Sources: D.A. Graff, Medieval Chinese Warfare, 300–900. Routledge 2002, pp. 162–178; H.J. Wechsler, "The founding of the T'ang dynasty: Kao-tsu (reign 618–26)" in The Cambridge History of China, Volume 3: Sui and T'ang China, 589–906, Part I. Cambridge University Press 2008, pp. 162–168.