The region was conquered by the Nanda Empire in the mid-4th century BC, and subsequently became part of the Maurya Empire. Ashoka, who was later a Mauryan emperor, was governor of Ujjain in his youth. After the death of Ashoka in 232 BC, the Maurya Empire began to collapse. Although evidence is sparse, Malwa was probably ruled by the Kushanas, the Shakas and the Satavahana dynasty during the 1st and 2nd century CE. Ownership of the region was the subject of dispute between the Western Kshatrapas and the Satavahanas during the first three centuries AD. Ujjain emerged a major trading centre during the 1st century AD.