We now consider how the military base area operated, as a zone where a large number of people lived and worked on a routine basis. On one hand, to function it required the affordances of its internal communications, connections with the civil town, and access to roads, river, and lands beyond the walls; on the other, there was a need for surveillance and control of activities within the base, and of movements across its boundary. The most obvious part of the base boundary (Plate XXII) is the substantial mud brick wall ploughed across four blocks from the city defences just S of Tower 21, and blocking Wall, A, C, and D Sts, with a gate established at B St. How the S boundary was defined E of D St has always remained an issue. If it was necessary to build a wall at the W end, why was this not simply continued all the way to, e.g., the S end of the Citadel? Across blocks F7 and F5 it seems that the boundary of the military zone simply comprised party walls between military and civilian-occupied structures. The same was true within block B2, by the Citadel, although the boundary probably comprised building frontages along Lower Main St. On the plateau, as the camp wall may have been a subsequent local enhancement, except where the amphitheatre formed part of it, the boundary may generally have comprised the rear walls of military-held houses lining the S side of 8th St—probably all properties from the city wall to H St. The course of the boundary along the W side of the inner wadi is unknown, but the base is suggested, as along 8th St, to have incorporated at least all properties lining the S side of the Wadi Ascent Road, if not encompassing all blocks on the wadi slope—in which case the boundary here may rather have comprised property frontages on K St. The base area was split by site topography into two major zones, the flat plateau, and the N branch of the inner wadi around the Citadel. Each was further subdivided.
“The City Wall of Xi’an”