Prince Trần Ích Tắc, a son of Trần Thái Tông who had secretly invited the Yuan through merchants at Vân Đồn, went over to the invaders with his family; Prince Trần Kiện also surrendered in Thanh Hóa.
Political
Trần Ích Tắc defects to the Yuan
- 15 March 1285
- Southeast Asia