Kautilya's Arthashastra 8.1.26

8.1.26

śaktimattarāś ca paurā jānapadebhyo nityāś cāpadi sahāyā rājñaḥ //

The school of Parásara say that of the distress of the people and distress due to bad fortifications, the latter is a more serious evil; for it is in fortified towns that the treasury and the army are secured; they (fortified towns) are a secure place for the people; they are a stronger power than the citizens or country people; and they are a powerful defensive instrument in times of danger for the king. As to the people, they are common both to the king and his enemy.