Question: What is the date of death of Minh Mạng's father?
Sentence (from "Gia Long"): From 1789, Nguyễn Ánh was once again in the ascendancy and began his northward march to defeat the Tây Sơn, reaching the border with China by 1802, which had previously been under the control of the Trịnh lords.
Relevant evidence: No