Final answer:
Emperor Ashoka was instrumental in the spread of Buddhism after his conversion, sending missionaries like his son to diverse lands and significantly influencing the growth of Buddhism in Asia.
Step-by-step explanation:
Emperor Ashoka was the Indian ruler who significantly promoted the spread of Buddhism after his own conversion. Following his transformative experience after the bloody battle of Kalinga, Ashoka embraced Buddhism and its teachings of peace and compassion. He then embarked on a mission to propagate the Buddhist faith throughout his empire and beyond. He sent missionaries, including his own son, to various territories such as Sri Lanka to share the teachings of the Buddha. The impact of Ashoka's patronage of Buddhism led to an increase in the religion's following not just in India but also in other parts of Asia, further reinforced by missionary monks and trade relations. Ashoka's conversion arguably constituted a pivotal moment in the history of Buddhism, enhancing its transition from a regional to a world religion.