Map of China during the period of <a href="https://en.wikipedia.org/wiki/Transition_from_Sui_to_Tang" class="extiw" title="en:Transition from Sui to Tang">transition from the Sui to the Tang</a>, 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 <a rel="nofollow" class="external text" href="http://www2.demis.nl/">DEMIS Mapserver</a>, which are public domain, other wise self-made. Sources: D.A. Graff, <i>Medieval Chinese Warfare, 300–900</i>. Routledge 2002, pp. 162–178; H.J. Wechsler, "The founding of the T'ang dynasty: Kao-tsu (reign 618–26)" in <i>The Cambridge History of China, Volume 3: Sui and T'ang China, 589–906, Part I</i>. Cambridge University Press 2008, pp. 162–168.
<a href="//commons.wikimedia.org/wiki/User:Cplakidas" title="User:Cplakidas">Cplakidas</a>
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<span class="int-own-work" lang="en">Own work</span>