नदीदुर्गं हि हस्तिस्तम्भसंक्रमसेतुबन्धनौभिः साध्यमनित्यगाम्भीर्यमवस्राव्युदकं च ॥ कZ_०७.१०.३२ ॥
nadīdurgaṃ hi hastistambhasaṃkramasetubandhanaubhiḥ sādhyam anityagāmbhīryam avasrāvy udakaṃ ca
河川要塞可用象柱、渡口/涉渡点、架桥与舟船来制服;河水深浅无常,且可引流或排干。
Natural defenses are not absolute; engineering, logistics, and timing (variable depth) convert terrain into a manageable problem.