Kautilya's Arthashastra 7.18.8

7.18.8

na ced anugṛhṇīyāt, kośadaṇḍābhyāṃ mitram anugṛhya ye madhyamadveṣiṇo rājānaḥ parasparānugṛhītā vā bahavas tiṣṭheyuḥ, ekasiddhau vā bahavaḥ sidhyeyuḥ, parasparād vā śaṅkitā nottiṣṭheran, teṣāṃ pradhānam ekam āsannaṃ vā sāmadānābhyāṃ labheta //

If the Circle of States is favourable to his cause, then he may aggrandise himself by putting down the madhyama; if not favourable, then having helped his friend with men and money, he should, by means of conciliation and gifts, win over either the leader or a neigbbouring king among the kings who hate the madhyama, or who have been living with mutual support, or who will follow the one that is won over (by the conqueror), or who do not rise owing to mutual suspicion; thus by winning over a second (king), he should double his own power; by securing a third, he should treble his own power; thus gaining in strength, he should put down the madhyama king.