 In 1821 , Minh Mạng sent two of his aides from central Vietnam to serve as education officials in the south . One of the objectives was that they would oversee the imperial examination process and education system , which would allow them to determine who would serve in the government as mandarins and therefore fill the southern ranks with men acceptable to the court . However , their attempts were either blocked or circumvented by Duyệt 's incumbent officials and they returned to the capital two years later in failure . In 1823 , one of Duyệt 's closest subordinates Tran Nhat Vinh , was indicted by one of Minh Mạng 's officials from Huế , who charged him with trading rice on the black market and operating a brothel . Duyệt put a stop to the legal proceedings and angrily tried to turn the tables , calling on the emperor to execute the accusing official . This ended in a stalemate , but a few years later , Vinh was transferred to northern Vietnam and later imprisoned while Duyet was unable to do anything about the matter in the south ; Vinh 's position was taken by one of the emperor 's men . In 1826 , Duyệt resisted the removal of a regional official by the palace , leading the emperor to criticise him in a proclamation declaring that court appointments came under the purview of Huế . The following year , Duyệt executed convicted criminals without informing the capital , leading the emperor to criticise him again , saying that " the ultimate authority to decide questions of life and death belongs to the court . " 
