first French missionary executed was Gagelin in October 1833, the second was Marchand, who was put to death along with the other leaders of the Saigon citadel which surrendered in September 1835. From then until 1838 five more missionaries were put to death. The missionaries began seeking protection from their home countries and the use of force against Asians. Minh Mạng pursued a policy of cultural assimilation of non-Viet ethnic groups which from 1841, through 1845, led to southern Vietnam experiencing a series of ethnic revolts. Ruling style Minh Mạng was known for his firmness of character, which guided his instincts in his policy making. This accentuated his unwillingness to break with orthodoxy in dealing with Vietnam's problems. His biographer, Marcel Gaultier, asserted that Minh Mạng had expressed his opinions about national policy before Gia Long's death, proposing a policy of greater isolationism and shunning westerners, and that Long tacitly approved of this. Minh Mạng was regarded as more nuanced and gentle than his father, with less forced labour and an increased perceptiveness towards the sentiment of the peasantry. Although he disagreed with European culture and thinking, he studied it closely and was known for his scholarly nature. Ming Mạng was keen in Western technologies, namely mechanics, weaponry and navigation which he attempted to introduce into Vietnam. Upon hearing of the vaccination against smallpox, he organised for a French surgeon to live in a palatial residence and vaccinate the royal family against the disease. He was learned in Eastern philosophy and was regarded as an intellectually oriented monarch. He was also known for his writings as a poet. He was known for his attention to detail and micromanagement of state affairs, to a level that "astonished his contemporaries". As a result, he was held in high regard for his devotion to running the country. When Minh Mạng died, he left the throne to his son, Emperor Thiệu Trị, who was more rigidly Confucianist and anti-imperialist than his father. During Thiệu Trị's reign, diplomatic standoffs precipitated by aspiring European imperial powers on the pretext of the "treatment" of Catholic priests gave them an excuse to use gunboat diplomacy on Vietnam, and led to increasing raids and the eventual colonisation of Vietnam by France. Nevertheless, during his reign Minh Mạng had established a more efficient government, stopped a Siamese invasion and built many national monuments in the imperial city of Huế. Successions