Which were the four castes of India?

There existed in ancient Indian society during the lifetime of Sakyamuni

Buddha over 2,500 years ago a caste system comprising priests, the

military and ruling, farmers and traders, and serfs.

The fourfold caste system was uber definitive, disallowing trespassing

of any form. The Buddha in the course of his lifetime had undertaken to

advocate equality among the castes. For, class distinction ultimately not

to be, all living beings possess the Buddha-nature.