Kautilya's Arthashastra 9.2.6

9.2.6

"prabhūtaṃ me śatrubalam, śatrubalena yodhayiṣyāmi nagarasthānam aṭavīṃ vā, tatra me śvavarāhayoḥ kalahe caṇḍālasyevānyatarasiddhir bhaviṣyatiṇ" "āsārāṇām aṭavīnāṃ vā kaṇṭakamardanam etat kariṣyāmiṇ" - atyupacitaṃ vā kopabhayān nityam āsannam aribalaṃ vāsayed, anyatrābhyantarakopaśaṅkāyāḥ - śatruyuddhāvarayuddhakālaś ca
- ity amitrabalakālaḥ //

When he thinks that he will have to make his strong enemy to fight against another enemy on account of a city, a plain, or a wild tract of land, and that in that fight he will achieve one or the other of his objects, just like an outcast person in the fight between a dog and a pig; that through the battle, he will have the mischievous power of his enemy's allies or of wild tribes destroyed; that he will have to make his immediate and powerful enemy to march elsewhere and thus get rid of internal rebellion which his enemy might have occasioned; and that the time of battle between enemies or between inferior kings has arrived, then is the time for the exercise of an enemy's forces.