Council were selected from the high-ranking mandarins of the six ministries and the academies. Gia Long handled the northern and southern regions of Vietnam cautiously, not wanting them to be jarred by rapid centralization after centuries of national division. Tonkin, with the administrative seat of its imperial military protector (quan tổng trấn) at Hanoi, had thirteen provinces (tổng trấn Bắc Thành), and in the Red River Delta, the old officials of the Le administration continued in office. In the south, Saigon was the capital of the four provinces of Cochinchina (tổng trấn Nam Hà), as well as the seat of the military protector. The citadels in the respective cities directly administered their military defense zones. This system allowed Gia Long to reward his leading supporters with highly powerful positions, giving them almost total autonomy in ordinary administrative and legal matters. This system persisted until 1831–32, when his son Minh Mạng centralized the national government. In his attempts to re-establish a stable administration after centuries of civil war, Gia Long was not regarded as being innovative, preferring the traditional administration framework. When Gia Long unified the country, it was described by Charles Maybon as being chaotic: "The wheels of administration were warped or no longer existed; the cadres of officials were empty, the hierarchy destroyed; taxes were not being collected, lists of communal property had disappeared, proprietary titles were lost, fields abandoned; roads bridges and public granaries had not been maintained; work in the mines had ceased. The administration of justice had been interrupted, every province was a prey to pirates, and violation of law went unpunished, while even the law itself had become uncertain." Foreign military relations During the 17th and 18th centuries, the Cambodian empire had been in decline and Vietnamese people migrated south into the Mekong Delta, which had previously been Khmer territory. Furthermore, Cambodia had been periodically invaded by both Vietnam and Siam. Cambodia lurched uneasily between both poles of domination as dictated by the internal strife of her two larger neighbors. In 1796, Ang Eng, a pro-Siamese king had died, leaving Ang Chan, who was born in 1791. When Gia Long unified Vietnam, Eng was given investiture by Siam in order to hold out Vietnamese influence, but in 1803, a Cambodian mission paid tribute to Vietnam in attempt to placate Gia Long, something that became an annual routine. In 1807, Ang Chan requested formal investiture as