凭险 píngxiǎn
[resort to strategically located place of difficult access] 凭据险要的地势
凭险抵抗
《梁书·武帝纪上》:“凭险作守,兵食兼资,风激电骇,莫不震叠。”
《新唐书·卢怀慎传》:“边徼之地,夷夏杂处,凭险恃远,易扰难安。”