Kautilya's Arthashastra 7.9.35

7.9.35

tulye puruṣabhoge vikramaḥ kleśasahatvam anurāgaḥ sarvabalalābho vā mitrakulād viśeṣaḥ //

When the friend of the conqueror and his enemy happen to possess equal population, their people may yet differ in possession of qualities such as bravery, power of endurance, amicableness, and qualification for the formation of any kind of army.