17.So it's really important that these are defensible, incredible numbers because they are such an important component of the long run fiscal tightening.
18.By militarily conquering territory to expand the frontier to more easily defensible Eastern terrain like the Alps or the Rhine or through diplomatically controlling external threats.
20.In addition, the mountains and rivers helped make areas of the country defensible against nomads and marauders. Therefore, it became a center of early and advanced civilization.