यदा मन्येत भावेन हृष्टं पुष्टं बलं स्वकम् । परस्य विपरीतं च तदा यायाद् रिपुं प्रति ॥ १७१ ॥
When he knows his own army to be cheerful in disposition and strong, and (that) of his enemy the reverse, then let him march against his foe.
english translation