Kṛṣṇasya asāṃnidhya-kāraṇaṃ — Śālva–Soubha-vṛttāntaḥ
Why Kṛṣṇa was absent; the Śālva and Saubha account
प्रकृत्या विषम दुर्ग प्रकृत्या च सुरक्षितम् । प्रकृत्या चायुधोपेतं विशेषेण तदानघ,निष्पाप नरेश! द्वारका एक तो स्वभावसे ही दुर्गम्य, सुरक्षित और अस्त्र-शस्त्रोंसे सम्पन्न है, तथापि उस समय इसकी विशेष व्यवस्था कर दी गयी थी
prakṛtyā viṣamaṃ durgaṃ prakṛtyā ca surakṣitam | prakṛtyā cāyudhopetaṃ viśeṣeṇa tadānagha niṣpāpa nareśa |
ವಾಯು ಹೇಳಿದರು—“ಓ ನಿರ್ದೋಷ ರಾಜನೇ! ದ್ವಾರಕಾ ಸ್ವಭಾವತಃ ದುರ್ಗಮ, ಸ್ವಭಾವತಃ ಸುರಕ್ಷಿತ, ಸ್ವಭಾವತಃ ಆಯುಧಸಂಪನ್ನ; ಆದರೂ ಆ ಸಮಯದಲ್ಲಿ ವಿಶೇಷ ರಕ್ಷಣಾ ವ್ಯವಸ್ಥೆ ಮಾಡಲಾಯಿತು।”
वायुदेव उवाच
Even when a realm is naturally strong—geographically secure, well-guarded, and well-armed—wise rulers still add special precautions when circumstances demand. Natural advantages do not replace vigilant responsibility.
Vāyu describes Dvārikā’s inherent impregnability and armament, and notes that, in the specific situation being discussed, additional defensive arrangements were implemented beyond its usual protections.