Answer:
Japan.
Explanation:
The Nam Viet Empire was a puppet state of the Japanese Empire that existed during 1945. It had a short existence, since it coincided with the end of World War II and the surrender of Japan.
After the Japanese took full control of French Indochina in March 1945, they weighed the idea for the establishment of puppet states in the former colonial territory. This idea came partly from the theoretical approaches of the so-called Co-prosperity Sphere of Greater East Asia, a large community of Asian states that would be built around Japan and in which it would be the center of it. Its creation, however, was made too late in World War II to have any influence.
