Kautilya's Arthashastra 5.6.7

5.6.7

āptapuruṣādhiṣṭhitau durgapratyantasthau vā kośadaṇḍāv ekasthau kārayet, kulyakumāramukhyāṃś cānyāpadeśena //

Both the treasury and the army shall be kept under the command of two reliable and confidential persons and in a single locality, either within the fort or at the boundary of the kingdom.

Cognates, princes, and other chiefs of the royal family may be employed in works such as the capture of a chief who, employed as a commander of a fort or the tracts of wilderness, has turned inimical along with a strong band of supporters; or they may be sent on an expedition full of difficulties, or to visit the family of the king's friend.