Kautilya's Arthashastra 7.4.16

7.4.16

yadā vā paśyet "mitram ākrandaś ca me śūravṛddhānuraktaprakṛtiḥ, viparītaprakṛtiḥ paraḥ pārṣṇigrāhaś cāsāraś ca, śakṣyāmi mitreṇāsāram ākrandena pārṣṇigrāhaṃ vā vigṛhya yātum" iti tadā vigṛhya yāyāt //

When a king is so fortunate as to have a powerful friend in front and a powerful ally (ákranda) in the rear, both with brave and loyal subjects, while the reverse is the case with he enemies both in front and in the rear, and when he finds it possible for his friend to hold his frontal enemy in check, and for his rear-ally to keep his rear-enemy (párshnigráha) at bay, then he may march after proclaiming war against his frontal enemy.