Kautilya's Arthashastra 7.18.12

7.18.12

karśanīyaṃ vāsya mitraṃ madhyamo lipseta, pratistambhayed enaṃ "ahaṃ tvā trāyeya" iti ā karśanāt //

When place and time are found unsuitable for success in the above attempt, he should, by peace, seek the friendship of one of the enemies of the madhyama king, or cause some traitors to combine against the madhyama; if the madhyama king is desirous of reducing the conqueror's friend, the conqueror should prevent it, and tell the friend: "I shall protect you as long as you are weak," and should accordingly protect him when he is poor in resources; if the madhyama king desires to rout out a friend of the conqueror, the latter should protect him in his difficulties; or having removed him from the fear of the madhyama king, the conqueror should provide him with new lands and keep him under his (the conqueror's) protection, lest he might go elsewhere.