 Under President Ngô Đình Diệm, Trí was the commander of I Corps where he was noted for harsh crackdowns on Buddhist civil rights demonstrations against the Diệm government.Trí later participated in the November 1963 coup which resulted in the assassination of Diệm on 2 November 1963.Years later, Trí was exiled by Nguyễn Cao Kỳ, the most powerful member of the junta, but when Nguyễn Văn Thiệu came to power, he was called back to command III Corps.