Kautilya's Arthashastra 7.7.30

7.7.30

paṇitas tasyāpakārasamartho vikrameta, anyathā saṃdadhyāt //

A king of superior power may request of an inferior the help of the latter's army in return for the payment of a share in the profit less than the cost of the army supplied; and the latter, if powerful enough to retaliate, may declare war, or accept the terms otherwise.