The Venue: The Fourth Buddhist Council (of the Mahayana tradition) was held at Kundalvana in Kashmir (widely believed by historians to be near present-day Harwan, Srinagar) during the 1st century AD.
The Patronage: The council was organized under the patronage of the Kushan Emperor Kanishka I, who was a great follower and protector of Buddhism.
Leadership: It was presided over by the eminent scholar Vasumitra, with the famous poet and philosopher Asvaghosa serving as the vice-president.
The Outcome: This council is historic because it marked the formal, definitive split of Buddhism into two major sects: Hinayana and Mahayana. Additionally, the core teachings and commentaries (the Mahavibhasha Sastra) were engraved on red copper plates and securely locked away in stone boxes inside a stupa built specifically for this purpose.
Answer verified by Quintessence Classes faculty — Karan Nagar, Srinagar.