Kautilya's Arthashastra 7.18.38

7.18.38

amitraṃ vijigīṣuṃ ca yat saṃcarati durbalam /
tad balenānugṛhṇīyād yathā syān na parānmukham //

When, owing to his own weakness, a friend seeks protection both from the conqueror and the latter's enemy, the conqueror should help him with the army, so that he never turns his attention elsewhere.