State building, expansion, and conflict differed in Japan and Vietnam. The Vietnamese attended Chinese style schools and had a Chinese style military. Resistance to the Chinese influence led to division within Vietnam (North and South). Japan was ruled by an aristocracy. The Monks resisted the attempt to reconstruct imperial authorization.
Once the military gained control, the feudal system began. A civil war broke out between the peasant and upper class in Japan. This led to Japan being divided into over three hundred smaller kingdoms. As I mentioned already, Japan did not start out with a caste system, but this social division is what led to the outbreak or civil war. Without the division, Japan may not have broken up into small kingdoms.
The culture of Japan and Vietnam were also influenced by the Chinese. The Japanese had a strict court system that was filled with gossip and emphasized the arts. The first novel was also developed. Power struggles within the country led to the establishment of the court system. In Vietnam, women enjoyed greater freedom and choice for dress. The architecture was very similar to the Chinese, and they enforced assimilation of people. The difference between Japan and Vietnam was that in Japan women never gained back the slight freedom they once had, whereas in Vietnam women gained more rights.