[Vietnamization] If there's only one book you read on Cambodia, this is it! WHEN THE WAR WAS OVER by Elizabeth Becker

Hanoi created an elaborate blueprint for moving ten million people from the more densely populated north to the south by the year 2000. The mentality of the Red River Vietnamese had not changed. They wanted to push farther south and west--which they did, finally, not through the New Economic Zones but by invading and occupying Cambodia two years later... [Chapter 9: Habits of War, p. 355]

See Vietnamization

Also, Demographic Vietnamization