Thirukkural – 875
One who is without an ally, and has enemies two,
should make an ally of one of those two.
தன் துணை இன்றால்; பகை இரண்டால்; தான் ஒருவன்
இன் துணையாக் கொள்க, அவற்றின் ஒன்று!
When one faces two enemies and has to fight without an ally, he should ally with the more suitable among the two enemies and defeat the other. This couplet is under the chapter Judging the enemy’s strength (பகைத் திறம் தெரிதல்).