Nguyen Dynasty was established in 1802 on the basis of defeating Tay Son Dynasty and owning the country with a larger territory than any previous historical periods. Since the King Gia Long opened his dynasty until the invasion by French colonialists in Vietnam, based on the inheritance of the sea-tendency thinking and the strategic vision under Nguyen Lords, the kings: Gia Long, Minh Mang considered the maritime areas as a very important part and the gateway of the country. The seas and islands situate in a strategic position on political and military fields towards the nation's sovereignty and security, an abundant natural resources which served for the development of the social economy and a system of natural waterways which easily connected with the regions inside the country and the countries in the world. Nguyen Dynasty actively enforced its ownership in the defense, economic exploitation, the organization of commercial activities and the development of the maritime transport. Nguyen Dynasty not only preserved and protected finnly the national maritime territory but also obtained benefits from it such as economic benefits, transportation, absorbing Western culture and especially, "powerful country" position and prestige in Southeast Asia at that time. Unfortunately, after the Kings Gia Long, Minh Mang, the next reigning kings were unwise, conservative and had a restricted view, they did not protect the maritime areas and consequently, the enemies invaded and made them into the pedals to attack Vietnam in the second half of the 19th century.