Ancient Fortifications Were Impervious
Neither Persians, Greeks, nor Chinese [circa 500 B.C.E.] achieved any marked improvement over the engineering techniques which had been employed by the Assyrians. Fortifications had, in fact, progressed about as far as available means would permit; the art of siegecraft had failed to keep pace. Save for a few exceptional instances of surprise, ruse, or betrayal, walled cities or fortresses were impervious to everything but starvation.
— The Encyclopedia of Military History, p. 18
