The Nanda dynasty ruled in northern part of the Indian subcontinent during the 4th century BCE, and possibly during the 5th century BCE. In 326 BC, Alexander invaded India, after crossing the river Indus he advanced towards Taxila.
Ashoka was a patron of Buddhism therefore he used many symbols that are relevant in Buddhism as motifs in the Ashokan pillar. According to Buddhist tradition, Buddha entered his mother’s womb in the form of a white elephant.