5. Although mountainous terrain surrounds the area under consideration on all sides, facilitating defense, there are many penetrable avenues of approach on the north, northeast, and east. Only on the south and southwest are there natural barriers or continuous fortifications at which the Germans could maintain a passive defense. 6. The economic resources of the region are insufficient to support a prolonged organized defense in the face of heavy and concerted attack. In particular: (a) Lack of oil would be the principal economic limitation upon military activity.