After the battle of Kalinga, Ashoka stuck to the rule of no violence because of seeing how many people he hurt and killed after the battle. So he didn't want anything like that to ever happen again. And to make sure that would never happen again he made it an official rule.
-Gupta packet page 239

Ashoka created 3 principles;
1. Ahimsa (not to hurt any living thing)
2. Tolerance (respect different beliefs and religions)
3. Peoples well-being (people being well treated and respected)
-Gupta packet page 239

This scenario is similar to the Mauryan Empire