Arthashastra
"प्रभूतं मे श्रेणी बलम्, शक्यं मूले यात्रायां च आधातुम्ण्" ह्रस्वः प्रवासः, श्रेणी बल प्रायः प्रतियोद्धा मन्त्र व्यायामाभ्यां प्रतियोद्धु कामः, दण्ड बल व्यवहारः इति श्रेणी बल कालः ॥
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).
english translation
"prabhUtaM me zreNI balam, zakyaM mUle yAtrAyAM ca AdhAtumN" hrasvaH pravAsaH, zreNI bala prAyaH pratiyoddhA mantra vyAyAmAbhyAM pratiyoddhu kAmaH, daNDa bala vyavahAraH iti zreNI bala kAlaH ॥
hk transliteration by Sanscript