抄録
A boundary line usually must be thought from the relation between the environs and internal part of nation. A boundary line is not always constant, so the line which was formerly Frontier has a tendency to become a boundary when a political organization is established. In this case, the strength of the internal power exercises an influence upon the establishment of a boundary line.
In Indochina, in the era of the racial migration, it is thought that there had been village states, and after unification of them, an ancient nation-state was created. The boundary line area was always affected by the strength of the central power of the nation. It remained as Frontier territory until it was colonized.
As the colonization of Indochina was pursued, France wanted to establish a clear supremacy, and tried to boundarize its frontier district. After the Second World War, Indochina has become an international Frontier territory under such conditions as two super powers from outside and the influence of Communism and the expansion of Nationalism inside.
In 1975, unified by communists, the nations in Indochina formed socialistic states, and more and more there appeared the Boundarization with neighbouring nations by their power influence.
