Syncretism of Buddhism in Eastern Asia

Buddhism mainly spread from India because of three people as I stated previously, and was greatly aided by many names that have been lost to history, but were still people with great spirituality and determination. What I wish to discuss today is what happened to the cultures once Buddhism sunk in as the dominant religion.
Though Buddhism is clearly and obviously a nonviolent religion, many of its practicioniors in Eastern Asia were not just violent, they were excessively violent, from the samuri in Japan, who were in constant warfare for over 400 years, to the Chinese empire, which was constantly expanding its borders in all directions, with few setbacks, to the three kingdoms of Korea, of which two of whom were almost constantly at war. At the same time, the emperors of China and Japan were devout Buddhists nearly all of the time, which is contradictary to the central tenent of nonviolence. Buddhism made the souls of the men who practiced war more at peace, giving them solace in the fact that they were spiritually sound even though they were attempting to cut someone else in half. Buddhism also made the cultures of Eastern Asia accept war less, and accept the hermit who lives in peace with his environment more. Eastern Asia has many temples that are secluded, for this very reason. Warfare was still pursued, yet it was pursued to gain power, as opposed to many Dark Age and medieval knights in Europe of the same time period, who fought for pure pleasure more often than not. This is part of the reason why China is very ethnocentric; other than the Middle Kingdom explanation, China also supported Buddhism, which encourages a lifestyle of aloofness with the rest of the world. This became part of China's cultural identity after multiple dynasties incoporated Buddhism in legitimizing their power.