You have also learnt why those two heroes are invincible and why they have not been ever vanquished in battle; as also why the sons of Pandu, O king, are unslayable in battle by anybody.
अवध्यौ च यथा वीरौ संयुगेष्वपराजितौ। यथा च पाण्डवा राजन्नवध्या युधि कस्यचित्॥