At the time of the Buddha, it had been absorbed into the kingdom of Kosala, and Pasenadi was king of both countries (D.i.288; M.ii.111). The Mahāvagga (Vin.i.28l), however, mentions a Kāsika-rājā (king of Kāsi?) who sent a robe to Jīvaka. Buddhaghosa (see Vinaya Texts ii.195, n.2) says that this was a brother of Pasenadi and son of the same father. He was probably a sub-king of Pasenadi. Pasenadi's father, Mahākosala, on giving his daughter in marriage to Bimbisāra, allotted her a village of Kāsi (Kāsigāma) as bath money (J.iv.342; J.ii.403; SA.i.110,120f, etc.).
Even at this time, however, the memory of Kāsi as an independent kingdom seems to have been still fresh in men's minds. It is very frequently mentioned as such in the Jātakas and elsewhere. Kāsi was once ruled by the Bhāratas, one of whom, Dhatarattha, was its king in the time of Renu (D.ii.235f).
There seem to have been frequent wars between the countries of Kāsi and Kosala, victory belonging now to one, now to the other. In one such war, Dīghāti, the Kosala king, was defeated by the king of Kāsi, but Dīghīti's son Dīghāvu won back the kingdom (Vin.i.334; J. iii.487; DhA.i.46). In another war the Kāsi king, Mahāsīlava, was taken captive by the ruler of Kosala, but his kingdom was later restored to him (J.i.262, etc.; see also i.409; UdA.123).
The traditional name of the king of Kāsi from time immemorial was evidently Brahmadatta, and references to kings of that name abound in the Jātakas. Sometimes the king is referred to merely as Kāsi-rājā.
The capital of Kāsi is generally given as Bārānasī, but it is said that when Asoka was king of Kāsi his capital was in Potali (J.iii.155), and another king, Udaya-bhadda, had his seat of government in Surundha (J.iv.104ff). It is possible that these cities did not form part of the regular kingdom of Kāsi, but became annexed to it during the reigns of some of the more powerful kings.
Kāsi was evidently a great centre of trade and a most populous and prosperous country. Frequent mention is made of caravans leaving Kāsi to travel for trade. One highway went through Kāsi to Rājagaha (Vin.i.212) and another to Sāvatthi (Vin.ii.10; Mhv.v.114). Kāsi was famed for her silks, and Kāsi-robes were most highly esteemed as gifts, each robe being valued at one hundred thousand. (See, e.g., J. vi.151, 450; see also Addhakāsi). Mention is also made of the perfumes of Kāsi (Kāsi-vilepana (J.i.355) and Kāsi-candana (A.iii.391; UdA.332)).
2. Kāsi, or Kāsika. A city, the birthplace of Phussa Buddha (Bu.xix.14; J. i.41). There he preached the Buddhavamsa (BuA.193). The city is probably to be identified with Benares, which is sometimes referred to as Kāsipura (E.g., DhA.i.71; J. v.54; vi.165; M.i.171; DhsA.35; Cv.xli.37). It is also called Kāsipurī (PvA.19).