Kautilya's Arthashastra 9.2.4

9.2.4

"prabhūtaṃ me śreṇībalam, śakyaṃ mūle yātrāyāṃ cādhātumṇ" hrasvaḥ pravāsaḥ, śreṇībalaprāyaḥ pratiyoddhā mantravyāyāmābhyāṃ pratiyoddhukāmaḥ, daṇḍabalavyavahāraḥ - iti śreṇībalakālaḥ //

When he thinks that the immense corporation of soldiers he possesses can be trusted both to defend his country and to march against his enemy; that he has to be absent only for a short time; or that his enemy's army consists mostly of soldiers of corporations, and consequently the enemy is desirous of carrying on treacherous fight rather than an actual war, then is the time for the enlistment of corporations of soldiers (srení).